Imaging and Printing Tech Tips
|If you are brand new to the world of digital imaging, you may want to start with my web based 'slide show' called The Home Digital Darkroom.|
Table of contents for this page:
Information About My Web Scans
JPEG Or GIF And Monitor Settings
Color Space, Color Bit Depth
ICC Color Managed Workflow
Basic Color Management in Photoshop 6.5 through CS
BASIC DIGITAL IMAGE EDITING
Adjusting And Working With Digital Images
PRINTING IN YOUR HOME DIGITAL DARKROOM
Resampling, Scaling, Printing And Dpi
Enlargement Size vs. Resolution Issues
Photo Quality Printers
Comments On Some Image Editing Programs
SOME IMAGE EDITING TIPS FOR
Burning And Dodging
Using Linear Gradient For Correcting Image Corner Light Falloff
Using Layers And Color Range To Control Color Density
Touch Up And Spot Removal With The Clone Tool
DIGITAL IMAGING FOR THE WEB, EMAIL OR COMPUTER SCREEN
Imaging For The Web Or Email Using JPEG File Format
Thumbnail And Image Size Issues For The Web And Email
Web site Links
SCANNING AND IMAGE CREATION
The Home Digital Darkroom
Professional Scans Or Your Own Desktop Film Scanner?
Film Scanner Or Digital Camera?
Formulas For Scaling DPI/PPI For Scanning Or Printing
Archiving Digital Images
------------------------------------------------------------------------------------------------------------------------------------------------------------This article is located on one web page. Almost all of the links are just jump links within the page. Use your browsers 'back' button if you want to get back to where you linked from. If you are trying to find a particular topic, use one of the 'return to table of contents' links.
Information About My Web Scans
Most of my Kodachrome 25 slides were scanned to Kodak Photo CD. The Kodak Photo CD scanning process did a very good job of capturing Kodachrome's vivid color, contrast range and image detail in the slides. The Kodak Photo CD saves each scan in five different sizes. 128X192 is the smallest size and 2048X3072 is the largest. This range allowed for a lot of choices and flexibility in the use of your image.
Unfortunately, Kodak's Photo CD is now discontinued. Even though Kodak is no longer supporting Photo CD, any professional level photo service bureau can scan your slides, negatives or prints to your required image resolution/s and return them to you on CD or DVD. Consumer photo labs may have limited choices when it comes to digitizing your film or print collection.
Scans made from slides or negatives have a much greater tonal and luminosity range than scans made from prints. Output from slide or negative scans will look more like the original photographed scene on a computer screen or print than output from a flat bed scan of a photograph would. It's my opinion that slide scans are actually the best media for computer screen images because slides are designed to be a back lighted medium.
From 1997 through 1998 I used the original Hewlett-Packard Photo Smart film scanner for scanning my 35mm film. My tests indicated that this very inexpensive consumer level device can produce scans equal to and in some cases better than the Kodak Photo CD. This is primarily because of the control I have in preparing the image during the preview scan before it is actually scanned to full resolution. With commercial scanning services you are at the mercy of the scanner operator for such important issues as density, color corrections and equipment cleanliness.
From 1998 to 2001 I used a Nikon LS2000 film scanner for 35mm media. The LS2000 scans slides and negatives at up to 2700 dpi and 36 bit color sampling. The LS2000 produces noise free professional quality scans with high color saturation up to 2400X3600 pixels in size. The LS2000 can scan to calibrated RGB or CMYK. The LS2000 is also capable of 48 bit color output. I am now using a Nikon Super Coolscan 4000 ED film scanner. This scanner has all the features of the LS2000 plus 4000 dpi optical resolution and 42 bit color sampling. It also has an enhanced hardware/software features that allow it to remove scratches and blemishes and minimize the appearance of film grain digitally during the actual scan.
I am using an Epson Perfection 2450 Photo scanner for my 4X5" and 6X9cm film scans. This flatbed scanner has an optical resolution of 2400 dpi and samples at 48 bit color depth. At 2400 dpi this scanner can produce files large enough to print at 300 dpi up to 30X40 inches from 4X5 transparencies and up to 18X26 inches from my 6X9cm transparencies. It can also do reflective scans of media up to 8.5X11.7 inches. In my opinion the 2450's fixed focus optics and staggered 1200 dpi CCD (2 X 1200 for 2400) make this scanner inadequate for 35mm film scans. - return to table of contents
JPEG or GIF And Monitor Settings
For displaying photographs on the web JPEG is much preferred over GIF file format. This is because GIF is limited to only 256 colors. GIF is fine for clip art and logos but most photographs will look layered where a color needs to blend from one shade to another. You should be using 24 or 32 bit color (also called 'true color') to see photographs in JPEG file format at their best. You will need to check your computer's screen setting adjustments to see if you can run 24 or 32 bit color depth at the screen resolution of your choice. If you are using Windows, just right click on any empty space on your desktop. Select properties from the drop down window and then select settings. In the lower right hand corner of this dialogue you will see a screen resolution setting slider. On the lower left hand side you will see the color selection drop down menu. Use the color selection drop down menu to select 24 or 32 bit True Color. Some newer graphics display cards offer 32 bit color as the only 'True Color' setting. See a screen capture image of Windows monitor properties setting dialogue box. - return to table of contents
In order to produce digital images that will print with colors and a tonal range that approximate what you see on your monitor, you'll need to do a basic monitor calibration. The simplest way to accomplish this is to adjust your monitor's gamma. To check and adjust your monitor's gamma level and color depth settings click on the following link to see a Gamma and Color Settings Check Chart. You should be able to see each individual shade from pure black to pure white and all the colors smoothly blending together without any banding or speckle like effects. You will probably need to use more than the test page's recommended 25% for brightness. I've found 50-80% brightness to be a more likely average setting. After this basic calibration is done it's usually not very difficult to get a feel for the adjustments you'll need to make with your imaging program's color and tonal range tools and your printer's tools to get a decent match between the printed output and the color and tonality of the image represented on your computer screen.
If you need to have exact color matching, you may want to consider buying a monitor calibration software/hardware solution. Monaco Systems, Eye One and other companies offer color calibration products that allow you to make an ICC profile based on your monitor's actual color characteristics. You can read more about ICC profiles and ICC color managed workflow two headings below in this document.
Those of you who are contemplating buying a flat panel monitor should know that mid to low end flat panels are a very poor choice for serious image editing due to the narrow angle of view, mediocre color accuracy and limited contrast range. Flat panel monitors intended for advanced image editing should have a contrast ratio of 500 to 1 or higher and have some sort of advertised 'wide angle view' capability. - return to table of contents
Color Space, Color Bit Depth
The RGB (red, green, blue) color space is the default for all consumer scanners and digital cameras. Another example of a color space is CMYK (cyan, magenta, yellow and black). CMYK is the color space of all printers that use inks. There are several calibrated versions of the RGB color space that encompass different areas and amounts of the visible color spectrum.
Scans done with the RGB color space produce image files consisting of these three colors blended together to produce all other colors as well as the different shades of red, green and blue. For the web and home digital darkroom RGB is the only color space you need to be familiar with. One of the newest calibrated versions of RGB is sRGB. The sRGB color space is a shared project of Microsoft and Hewlett-Packard. It is designed to help make color matching between computer screens and the latest generation printing devices easier to do. sRGB has a color gamut that doe not match the color gamut of most types of commercial printing inks very well. It may not be the best choice when the output will be for offset press generated publications. Microsoft and Hewlett-Packard think sRGB solves a lot of color matching problems in a home digital darkroom environment that is not using ICC color management. sRGB is certainly the best choice when your output is going to be used mainly for presentation from a computer monitor (web site placement, email, PowerPoint etc ).
You will need an imaging program that has color management options to be able to choose between sRGB and other calibrated RGB color spaces. The lower end programs may use either sRGB or their own un-calibrated version of RGB without telling you which of these color spaces is actually being used. Programs that have color management options will usually allow you to choose the exact color space you want to work with. I find that I prefer to work in sRGB for my web imaging and Adobe RGB for my Epson printers. sRGB does make the best color match for computer screen viewing in graphics viewers and web browsers. Some of the home photo printers by both HP and Epson are actually optimized for sRGB images. If you aren't using an ICC profile workflow, try sending the same photo to your printer in sRGB and Adobe RGB and see which print you like best. We will discuss calibrated color spaces and ICC workflow in more detail in the next section of this article.
There is also a "bit depth" to digital image files. Each pixel recorded during the scan has color information assigned to it. Each pixel's color information is saved as a number of bits (8 bits = one byte) for each color channel (red, green, blue). Depending on the quality of the scanner it can save from 8 bits to 16 bits per color channel for each pixel recorded. Most of the consumer scanners save 12 bits per channel. Multiply this figure by 3 (for each color channel red, green and blue) and you get the color bit depth of the scanner. A scanner that can save 12 bits of color information for each color channel per pixel is a 36 bit scanner. A scanner that can save 14 bits of color information for each color channel per pixel is a 42 bit scanner. All of the current 12 and 14 bit scanners are 'interpolated' up to 48 bit color output (16 bits per color channel). We will discuss the merits of 48 bit color in more detail in the next paragraph of this document. The higher color bit depth scanners can produce a broader range of colors and tonality.
Since computers can only deal with multiples of 8 bit "computer words" (1 byte), scanners must interpolate the number of bits up or down and/or add null bits (zeros) to make the scanned pixel's color information available to the computer and imaging program as either 24 bits (three 8 bit words or 3 bytes) or 48 bits (6 bytes). A 30 bit color scanner will produce 24 bit color files. A 36 or 42 bit scanner can interpolate up or down to produce either 48 bit or 24 bit color files.
48 bit color can only be saved as TIFF files. Working with 48 bit color images is only supported by a few high end imaging programs like Adobe Photoshop and PhotoImpact ( limited 48 bit color editing in PhotoImpact). Adjusting your image color and tonality while it is in 48 bit color will provide smoother gradations between colors. After all color and tonal range adjustments have been completed the image can be converted to 24 bit color for printing or monitor presentation. This conversion down to 24 bit does not negate the advantage of adjusting color and tonal range while the image is in 48 bit mode.
It doesn't take a math genius to see that 48 bit image files are twice the size in kilobytes or megabytes as 24 bit image files. 48 bit color is the future of digital imaging. All of today' scanners and almost all of the high end digital cameras that can output RAW files are capable of producing 48 bit color image files. As computers become more powerful and hard drives become larger, the larger file sizes of 48 bit images and the longer image processing times are just not the issues they used to be. I find it hard to believe that so few of today's image editing programs support editing in 48 bit color mode. For now, editing in 48 bit color is most appropriate for fine art photographers and photographic service bureaus that can afford Photoshop.
Scanners and computer screens and digital cameras operate in the RGB color space but printers use inks in the CMYK color space. Fortunately for the home digital darkroom enthusiast, converting RGB to CMYK and producing accurate color prints is not the nightmare it used to be. All current home color printers accept RGB data from your imaging program and convert to their CMYK output automatically. Professionals preparing scanned images for offset press output may still do this conversion manually. - return to table of contents
ICC Color Managed Workflow
If you are really fussy about color matching you may want to investigate the possibility of using an ICC color managed workflow (ICC profiles) in your home digital darkroom. ICC profiles are basically calibrated computer file color maps that optimize color matching between your monitor, scanner, digital camera, printer and specific photo paper. Each device can have its own ICC profile. Many digital cameras and most scanners can also output image files with a calibrated color space. See the International Color Consortium web page to learn more about ICC workflow history and new developments.
The first step in ICC workflow is to work in a calibrated color space. Adobe RGB 1998, sRGB-IEC61966-2.1, Apple RGB, Color Match RGB are all examples of calibrated color spaces. Each of these color spaces has a color gamut or range of colors it can reproduce. High end scanners and digital cameras will allow you to choose a calibrated color space to create your images in. Also, mid to high end digital image editing programs will allow you to select a calibrated color space to work in. To insure proper color management you would use the same calibrated color space in your image editing program that you selected in your digital camera or scanner. Adobe RGB 1998 is a favorite for photographers because it has a slightly wider color gamut than most printers can handle. This approach insures that you can take advantage of all the colors that your printer is capable of producing.
The color gamut for sRGB is smaller and optimized for the colors a computer monitor can reproduce. Many home inkjet photo printers are optimized for sRGB. The logic for that approach is that most people are not using an ICC workflow and sRGB is a better choice for color matching between monitors and printers in an un-calibrated workflow. However, most high end digital cameras and scanners are capable of outputting a wider color gamut than exists in sRGB. These wider gamut colors cannot be reproduced accurately, even with a wide gamut photo printer, when saved in the sRGB color space. If your digital camera or scanner allows you to work with calibrated color spaces, save your images as Adobe RGB 1998. You can always convert an Adobe RGB image to a lesser gamut like sRGB. Converting an sRGB image to a wider gamut color space doesn't produce a broader range of colors.
Monitors and scanners need to have profiles made for each individual piece of equipment. To generate a monitor profile you would buy a monitor color calibration hardware/software package. These products incorporate a device that fits on your monitor screen and reads the actual colors produced by your monitor. The software part of the package then interprets the difference between your monitor's color output and what it SHOULD be outputting. The difference is accounted for in the ICC profile that the monitor calibration software generates and installs in your computer's operating system (Windows XP and Mac). After the monitor profile is installed your video card reads the profile and adjusts the monitor output to be visually correct. Photoshop comes with a simple monitor calibration routine that relies on visual interpretation. It is called Adobe Gamma. After Photoshop is installed this calibration program is available to run from the 'control panel' of the Windows OS. Eye One and Monaco Systems have very capable monitor calibration packages. Both of these basic monitor calibration programs are under $200.
To generate an ICC profile for your scanner you need to have scanning software that accepts ICC profiles and software to run an IT8 calibration routine. IT8 calibration uses a calibrated color transparency test pattern or a calibrated reflective color test pattern (also called Q60 targets). The scanner calibration software reads the test pattern and compares the scanner's un-calibrated output colors to what they should be and generates an ICC profile that accounts for the difference. The IT8 calibration generated ICC profile is then installed in your scanning software and the scanner's un-calibrated color output is adjusted to produce proper colors for your preview image and scan. Saving the resulting scans in a calibrated color space insures color matching between scan preview and the scanned image when it is opened in a properly configured ICC compliant image editing program. A couple of aftermarket scanner control applications that support IT8 calibration are SilverFast and VueScan. I have a mini-review of these two After Market Scanner Control Software applications.
The last step in an ICC workflow is to have an output ICC profile for your printer and photo paper type. Output profiles are available from printer and photo paper manufacturers and from commercial photo printing services for their LightJet, Chromira, Fuji Frontier and other high end laser and LED printers. Eye One has a calibration product that will allow you to profile your monitor and your own printer with any paper you choose for about $1500. The required output ICC profile is selected in your image editing program after you decide which printing device and paper that particular image is going to be printed on. Output profiles for printers and papers only work properly if your printer driver has an ICC or ICM (image color management) mode. Many of today's high end inkjet photo printers have an ICC output mode. However, some printers only allow you to pick a calibrated color space like Adobe RGB or sRGB under their color management properties. Check your printer's documentation or properties to make sure it has a setting in its color management properties to accommodate ICC (ICM) mode before you go to the expense of buying software that will make an ICC profile for a printer.
If you intend on using the photo for web, email or any other computer presentation, use sRGB as your working space. If you are using Adobe RGB for your working space, convert to sRGB for web, email or monitor presentation.
Photoshop from level 6 through CS2 provides excellent tools for ICC workflow. Other image editing programs provide a limited amount of calibrated workflow but most don't even come close to Photoshop's full featured and versatile implementation of ICC workflow. - return to table of contents
Basic Color Management in Photoshop 6.5 through CS
The following color management procedures are dependent on a properly calibrated monitor. Use Adobe's Gamma routine or purchase an aftermarket monitor calibration hardware/software solution.
You'll also need to have ICC profiles designed specifically for your printer and photo paper combination. Epson includes ICC profiles with the printer software for almost all of their photo printers and papers. If you use Canon or HP inkjet printers you'll need to check your printer's documentation for the availability of ICC profiles. Many aftermarket inkjet photo papers also make their own ICC profiles for some of the more popular Epson and Canon printers. Ilford, Pictorico, Moab Papers, and Red River Papers are just a few that I know of who make ICC profiles available to download for their inkjet photo papers. Currently, Epson's UltraChrome pigmented ink printers have the best selection of aftermarket ICC profiles. As mentioned in the preceding section on ICC workflow, you can buy a color management hardware/software calibration solution that includes the ability to make profiles for any printer/paper combination.
1. Configure the Color Settings dialog box - A. Select Edit>Color Settings. B. Click the 'Advanced' checkbox. C. Select Adobe RGB (1998) from the Working Spaces 'RGB': dropdown list. D. Select 'Preserve Embedded Profiles' from all dropdown lists under 'Color Management Policies'. E. Select 'Perceptual' from the Intent: dropdown list under 'Conversion Options'. F. Check the 'Black Point Compensation' and the 'Dither' options. G. Keep the 'preview' checkbox enabled and click OK.
2. Scanner image import A. Select File>Import> your scanner plug-in. B. Scan an image using the Acquire or Twain module for your scanner. If your scanner software has color management, set the output color space to Adobe RGB 1998. Name and save your scanned image. We recommend that you work from a copy of the saved scan. This provides you with an original of the image in your selected RGB working space. This may be useful should you desire to re purpose the image later on.
3. Assigning an input profile - If your image is from a profiled scanner, assign your input profile - Select - Image>Mode>Assign Profile, select the 'profile:' radio button, then select your scanner profile from the profile dropdown list. For Photoshop CS2 select Edit>assign or convert to profile
If you are not working with a profiled scanner or your scanner software did not allow you to export an image tagged with a working color space, select the 'Working RGB: Adobe RGB (1998)' radio button for images that you want to print. You can select the radio button 'Profile:' and select sRGB IEC61966-2.1 from the dropdown list if you know you only want to use the image for computer monitor presentations like email and web placement. sRGB has a color gamut that more closely matches the colors on a computer monitor. Adobe RGB 1998 has a wider color gamut then sRGB and is more appropriate for images that you intend to print A 'tagged' image has information that describes the exact color gamut (color space) to color management enabled imaging applications.
If you toggle the Assign Profile window's 'preview' checkbox on and off, you can view the effect of your input profile on the image. Keep the 'preview' checkbox enabled and click OK. When you Assign an input profile to an image, Photoshop uses the profile to interpret the image data. Color values are not altered.
4. Digital Camera Images - For color management to work reliably your digital camera must be able to 'tag' JPEG images with a working color space. When shooting RAW, your RAW converter should be configured to tag and save the resulting TIFF or JPEG files with a working color space, preferably Adobe RGB 1998. All of the current popular OEM and aftermarket RAW converters have color management capability.
5. You can now edit your scanned and tagged image or tagged digital camera image.
6. When editing is complete, you have TWO CHOICES to set up for printing. The first method is to convert your image's color space to a profile designed for a specific printer and paper. The second choice is to have Photoshop temporarily apply the new printer/paper profile before it sends the image to your own printer.
If you use the 'convert to profile' method be sure to do a 'save as' for the newly converted image before you convert to profile. 'Convert to profile' permanently alters the image's color gamut. The 'convert to profile' choice is probably most appropriate when you are sending images out to be printed at a service bureau that has made downloadable output profiles available for their printer.
To Convert to Profile: select - Image>Mode>Convert to Profile. A. Select your printer/paper profile from the 'profile:' dropdown list. B. Select Adobe (ACE) from the Engine: list. C. In the 'Intent:' dropdown list select the rendering intent appropriate to your image. If you are printing a photographic image, select Perceptual. D. Check the Black Point Compensation E. Select OK. Photoshop converts the image data to the color space of the printer/paper profile you selected.
7. Printing the image. A. Select File>Print with Preview and click 'show more options'. B. Click 'Page Setup' and select your photo printer and click on properties. Select your paper type, size and orientation and other printer specific setup details.
In your printer's 'color management', depending on your printer's software interface, select ICM with no color management (Epson 2200) or No color management (Epson 4000). Click OK all the way back to the Photoshop Print Preview window. Make sure 'color management' is selected in the Photoshop Print Preview window. If you DID the CONVERT TO PROFILE step make sure the 'source space' is set to 'document' (your printer/paper profile) and the 'print space' is set to 'same as source'. If you DID NOT do the convert to profile step, make sure the 'source space' is set to 'document' (your color space) and the print space is the proper profile for your printer/paper. Set the intent to perceptual and check the 'use black point compensation' box. You are now ready to PRINT!
If you want to use Photoshop's soft proof (view your image in Photoshop with the printer/paper output profile applied) do the following: Go to View>proof setup>custom. In the 'device to simulate' box select your printer/paper profile. In the rendering intent box select 'perceptual' and check the 'black point compensation' box. In the display options select 'simulate paper color'. Now select OK. You can toggle back and forth between the soft proof rendition and normal image by selecting and then deselecting View>proof colors. Soft proofing is somewhat open to visual interpretation and it takes some practice to take full advantage of this feature.
Much of this section on color management in Photoshop was copied or paraphrased from a Monaco Systems PDF document on color management with Photoshop 6. This document is no longer available on their web site. - return to table of contents
If you plan to send your digital files out to a professional service bureau like West Coast Imaging or NancyScans, be sure to download their ICC profiles and instructions on how to set up your digital files for their printers. Click the following link to see a very informative and easy to read PDF Slide Show by Adobe's James C. King. This PDF document discusses the advantages and basic structure of an ICC workflow with a nice text + graphics presentation.
Be aware that some profiles, including some manufacturer supplied profiles and monitor calibration generated profiles, are not very good. The most important step in this workflow is monitor calibration. If this is not done properly, you can not correctly assess whether or not printer/paper (output) profiles are accurate.
The most frequently recommended monitor color temperature for photographic reproduction is 6500K. 5000k is too warm for most print viewing conditions and the Windows monitor default of 9300K is just a little too cool when compared to average print viewing conditions. 7500K would also be an acceptable color temperature selection when calibrating your monitor - return to table of contents
Comments On Some Image Editing Programs
Photoshop at 6 through CS3 has an excellent selection of tools and professional level features for the RGB imaging enthusiast. The quality of Photoshop's tools and the ability to work with 48 bit images, handle calibrated color spaces and support an ICC profile color managed workflow make Photoshop the best choice for professional photographer. Photoshop is also suitable for amateur photographers who need or want the best imaging program available today. Cost; retail boxed list about $600.00
Adobe Photoshop Elements has most of the basic tools that Photoshop has but will not edit 48 bit images (converts to 24 bit color upon opening). Elements has limited color management workflow tools. Elements seems to have the same excellent image manipulation algorithms as Photoshop. Elements 3 now includes a camera raw file converter. Cost; retail boxed about $100.00
Paint Shop Pro will open most 48 bit images but coverts them to 24 bit upon opening. Paint Shop Pro has limited color management workflow tools. Paint Shop Pro has a very full featured toolbox. Cost; retail boxed about $90.00 downloaded about $80
PhotoImpact has a huge variety of tools, options and extra features. PhotoImpact will allow color and tonal adjustments on 48 bit images. It also has limited color management workflow tools. This program is a bit of a memory and resource hog. Don't buy this program if you don't have at least 512mb of RAM and a PIII of 400mhz or faster. I'm sure it will work with less RAM and a slower processor but it might be 'painfully' slow in getting most jobs done with high resolution files. Cost; retail boxed about $90.00 downloaded about $80
There are also image viewing and cataloging programs. These programs allow you to quickly find and view the images you have stored on your hard drives or CDROM's without waiting for a complex image adjustment program to open on your PC. Two of the best of these are ACDSee and ThumbsPlus
I'm currently using Photoshop CS2 for all of my image editing and printing needs. Many of these programs are available as downloadable evaluation software. You can try a program for free and decide if it is appropriate for your needs before having to pay for the program. You can click on any of the product links above to learn more about each of these program's features or download a time limited evaluation copy of the software.
The Home Digital Darkroom
A digital darkroom consists of three items: a true photographic quality printer and a scanner or digital camera and a graphics program like any of those described on this page. You can get by with a flatbed scanner, but you will lose some color depth and luminosity scanning photo prints. I prefer to scan transparencies and negatives with a dedicated film scanner.
Professional Scans Or Your Own Desktop Film Scanner?
I paid for color corrected film scans on my Kodak Photo CD and most of the time the color was spot on. However, the Photo CD work station operator occasionally missed the 'exposure' (white and/or black point setting) by a half to full stop. Also, there were always a quite a few dust spots on the scans. These kinds of problems with commercially done scans are common and with few exceptions were easily corrected with any graphics editing program.
The problem Photo CD images were the ones that were "over exposed" digitally and significant highlight detail was burned out and lost. If shadow or highlight detail is lost during a scan, you cannot get it back except by re-scanning the slide or negative. Now that I am using my own desktop film scanners I have full control over the color and tonal characteristics of the image I'm scanning. I usually have very little corrective work to do on the image file after the scan. Quality control issues aside, if you plan on doing quite a bit of scanning, a film scanner will save you money in the long run over commercial scanning services. The quality of scans from most of the older flatbed scanners with accessory transparency adapters is usually quite poor.
The best home imaging solution for film camera users is to use a dedicated film scanner. If you shoot both 35mm and medium format films, get a film scanner that handles both 35mm and medium format. The 5500X3600 pixel images produced by my Nikon Super Coolscan 4000 ED 35mm slide/negative scanner can be printed with photo quality up to 12X18 inches and beyond. My Epson Perfection 2450 Photo flatbed has an optical resolution of 2400 dpi and has a built in transparency adapter in the lid of the scanner. This scanner does an excellent job with large format film and a very nice job with medium format film. Since this scanner is fixed focus and has a staggered CCD to achieve it's 2400 dpi rating. It may not be the best choice if most of your scans are going to be from 35mm film. This scanner can produce files large enough to print at 300 ppi up to 30X40 inches from 4X5 transparencies and up to 18X26 inches at 300 ppi from my 6X9cm transparencies. It can also do reflective scans of media up to 8.5X11.7.
Kodak's current digital media offering is called Picture CD. Picture CD has built in features catering to the amateur home digital photo enthusiast. Features available on Picture CD include simplified support for sending photographs via email and the posting of your images to a web site as well as very basic image manipulation software. Picture CD must be ordered from Kodak at the time you develop your film. You get both prints and the Picture CD returned to you. Photo labs and service bureaus that cater to professionals will digitize your images to your required image resolution and save them to CD or DVD when you get your film developed. - return to table of contents
Film Scanner or Digital Camera?
Technical advances in digital photography have occurred at a phenomenal rate over the last few years. Digital camera photography has become a viable and even desirable alternative to film photography for many photographic situations. Photojournalist have long since left film behind. Most reportage type magazines have supplied their photographers with high end Digital SLR (DSLR) cameras and have adopted a digital workflow. Many fashion photographers are using Canon 1Ds 11mp DSLR cameras. The newer Canon 1Ds Mark II 16.7 mp DSLR should find an even greater acceptance with professionals. Wedding and portrait photographers are also moving to a digital workflow with 6 to 16mp DSLR's. It is widely accepted that 6mp DSLR's can make images that equal the visual quality of 35mm film images scanned at 4000 dpi. 11 to 16mp DLSR output is competitive with medium format films, the old standard for "professional" photographic output. See my article called DSLR vs. Film Scans for more information and six pages of comparison images.
With the current state of DSLR camera technology there are not too many arguments for investing in a 35mm SLR film camera outfit. Two exceptions would be budget constraints with the higher initial cost of the DSLR body or lack of interest in learning digital technology. A decent 35mm SLR camera body can cost as little as $300. A starter DSLR body is going to be more like $700 - $900. The budget issue gets a bit more sticky if you are only shooting 35mm and ultimately plan to digitize your 35mm film images. A good film scanner will put a $400 to $1200 dent in your wallet so you may be better off just jumping on the DSLR bandwagon after all. Another argument for a film and scan workflow is that there is at least 20mp worth of image information in any given film image. With the DSLR image you have to interpolate up from 6 or 16mp to equal that level of image resolution. The bottom line is you only have 6 to 16mp of original image information with current DSLR workflow. As DSLR technology continues to advance, you'll need to buy a new DSLR body when you want to take advantage of newly available increases in image resolution (more megapixels). After upgrading to a higher megapixel body, all of your previous DSLR images will be of lesser resolution and there will always be limits to upward interpolation of digital images. All of your film images will have the equivalent of at least 20mp of image information today and 20 years from now. This argument has a little less value if you are working exclusively with 35mm film since current 6mp DSLR images can be interpolated up to 20mp and be competitive with scanned 35mm film images. 35mm film probably tops out at about 20mp of useful image information.
The bottom has fallen out of the medium format camera new and used equipment market because most professional photographers are moving to DSLR's and an all digital workflow. However, for situations that require ultimate image detail, medium format 6X7cm and 6X9cm film scans from high end dedicated film scanners with focusing lenses contain more detailed image information than images from Canon's 1Ds 11mp DSLR or Kodak's newest 14mp DSLR. My most recent tests indicate that the new Canon 1Ds Mark II with 16.7 mp may equal or exceed 6X7 and 6X9 scanned image quality.
Can DSLR's compete in the 'fine art' and landscape photography realm when extremely large prints are needed? In my opinion none of the current DSLR's can compete with large format (4X5" and larger) film images when it comes to reproducing very fine detail. 4X5 is still the accepted king of the hill for landscape photography and prints larger than 16X24 inches. If you are the kind of person who enjoys seeing detail in each and every blade of grass and leaf in your landscape photography prints, 4x5 is for you. If you want to maximize depth of field by controlling the plane of sharp focus, 4X5 is the only alternative. If you need to control converging lines and other perspective issues in architectural photography, 4X5 is the way to go. 4X5 film scanned on high end consumer scanners or professional drum scanners produces detail rich images with a smooth and beautiful tonal range. 4X5 images from fine grained films like Velvia F, Provia F 100 and Astia F make prints that show very little, if any, film grain up to 20X24 inches. 4X5 film scanned at only 1200 dpi makes a 22mp digital image and those 22mp are scanned from an image area that is about 20 times larger than the image area of a full size sensor equipped DSLR.
This "Image magnification" factor gives us one more issue to consider when deciding if a DSLR will work for professional level landscape photography and large prints. An image sensor of about 1 square inch requires super excellent optics if the resulting images are going to be made into big prints. To make a 16X20 print from a 35mm film camera image or full frame DSLR image requires almost 20X magnification of that image. Even if we had a full frame sensor DSLR with 22mp resolution, the optics of the system become the limiting factor. This is especially true for the wide angle view. I love my Canon 16-35mm L zoom but its optical quality degrades as you move from the center of the image to the edges or corners. This image quality falloff is easily seen in 12X18 inch prints. My Canon 20mm f2.8 prime had some center to edge image quality falloff too. My Rodenstock 65mm large format lens also suffered a little bit of image quality degradation toward the corners. A 65mm lens on a 4X5 is about the same as an 19mm lens on a 35mm SLR. However the center to edge image quality falloff in my 65mm Rodenstock was considerably less than my DSLR (35mm) wide angle zoom lenses. Also, since my 4X5 images only need 4X enlargement to reach 16X20, the small image quality difference center to edge is hardly noticeable even in very large prints.
The other side of the DSLR vs. large format for landscape/fine art photography argument - if image content in your photography is most important to you, more important than extreme technical excellence in large prints - If you enjoy the 'long telephoto' view in your landscapes (4X5 telephoto photography beyond the 35mm equivalent of about 135mm is limited and expensive and requires a very long accessory bellows) - if traveling light and speed of setup is necessary for your photographic style - DSLR landscape photography may be your best choice. Actually my Canon 1Ds Mark II compares very favorably to 4X5 Velvia scanned on my Epson 2450. The 1Ds Mark II's 16.7mp may be enough for very large prints with some types of landscape image content. It is certainly competitive with 4X5 film with prints that are 16X24 inches and smaller.
If you aren't ready for a digital camera and pure digital workflow yet, the selection of lenses and equipment available in a 35mm SLR, medium format or 4X5 view camera outfit insures all the photographic flexibility needed to capture any type of image. Film scanners in the 3200-4000 dpi range allow you to print very big prints at photo quality from just about any film format. Prints from home inkjet photo printers look great. Prints from the newest professional level inkjet printers and prints from commercial digital photo printers like Frontier, Noritsu, LightJet and Chromira are as good or better than the best optical wet darkroom prints.
It is important to know that high megapixel resolution is not the only criterion for a good digital camera image. Current point and shoot digital cameras in the 5 to 8mp range have very small sensor arrays, about the size of a postage stamp. These sensors produce images that have noticeable digital noise, even at low to mid ISO settings. Digital noise looks a lot like film grain and can give an image a speckled or mottled look. Higher ISO rated film produces relationally more noise then lower ISO rated film. Higher digital camera ISO settings produce relationally more noise than lower digital camera ISO settings. Film grain or digital noise is hardly noticeable in snapshot sized prints. Film grain or digital noise detracts from image quality in larger prints.
Mid priced point and shoot digital cameras have limited lens focal length and shutter speed availability. Other advanced features such as exposure modes and off camera flash support are also sometimes limited with mid priced point and shoot digital cameras. Auto focus and shutter lag time take much longer in point and shoot cameras. This delay from shutter press to actual photo taking makes it hard to 'capture the moment' such as the perfect smile during a casual portrait session or any sort of action photography. If your main interest is in family and travel photography, point and shoot digitals in the 5 to 8mp range can work quite nicely. Point and shoot digitals are great for small to mid size prints and even larger prints if you don't mind a little 'grain effect' in your prints.
Digital SLR's have much larger sensor arrays than point and shoot digital cameras and these larger sensors have better sensitivity to light at every ISO setting. Canon and Nikon's DSLR's make images that are nearly free of digital noise at ISO speeds up to 400. DSLR's can use of all the lenses and accessories that were designed for the corresponding manufacturer's 35mm SLR cameras.
Whether or not digital prints are 'true photo quality' is a matter of personal opinion when it comes to prints generated for your own use. Some people are very happy with 8X10s from 2.5 to 3.3 megapixel cameras. The quality of prints from 5-8mp digital cameras can be competitive with prints from 35mm film scans at 2800-4000dpi.
Another consideration in the film vs digital debate is the knowledge needed to take advantage of digital imaging technology. You can use a digital camera for your travel and keepsake photography and you don't have to build and learn how to use a 'home digital darkroom'. Just take your memory card down to Walmart or Longs and use their digital kiosks. Insert the card in the digital photo kiosk, view the photos and make any size print from any given image. Gone is the expense of film and processing and the inconvenience of getting 24 or 36 prints, of which, usually only a few are keepers. If you want to send digital photographs as email attachments, or if you want to make different size prints at home and adjust their color and tonality, you'll need to hit the books, read some web site digital imaging tutorials or take a class in digital imaging technology. If you are just starting down the digital photography road, check out my Beginner's Level Digital Darkroom Tutorial.
The initial investment for a home digital darkroom can be low to moderate for a basic setup. If you already have a digital camera, all you need is a photo printer and software. Both items can be bought for less than $200 total. If you need a high end film scanner and a prosumer level printer, expect to give up $600 to $3000.
Another major consideration is how to archive your image collection. For film and prints a fireproof safe would be ideal but an old shoe box will do. It's much more complicated in a pure digital workflow. You can save your digital images to CDROM or DVD but in 20 years will you be able to read that optical media with the computer systems available in the year 2025? More importantly, will your grandchildren be able to read that media? Will you be able to organize and categorize your digital image collection so that you or someone else can find a specific image or image type out of thousands of saved images?
If you really want to archive your digital images you'll need to migrate your image collection every 10 years or so to the latest storage media. At some point you may even want to consider appointing a 'trustee' who will be responsible for keeping your digital image collection accessible in the years to come.
I recommend spending some time reading and posting questions to the Usenet news groups rec.photo.digital, comp.periphs.scanners and comp.periphs.printers before you decide what type of equipment to invest in for your own digital darkroom. If you don't know how to access Usenet using 'news reader' software like MS Outlook Express, you can also read and participate in these newsgroups from a web interface in Google's Groups.
The most popular type of scanner is the flatbed. This type of scanner has a glass top with a lid for scanning reflective material like photographs and magazine pages or other print material. Flatbeds also come in handy for faxing and OCR scanning. OCR (optical character reading) is where you scan a printed document and the OCR software converts the bitmapped image of characters (the ABC's) in the scanned document into the actual characters in a program like Word or Word Perfect.
Another type of scanner available to the home user is a film scanner. This scanner is used for scanning slides and negatives. To quote from the beginning of this page, "Slide and negative scans have a much greater tonal and luminosity range than scans made from prints. Output from slide or negative scans will look more like the original photographed scene on a computer screen or print than output from a flat bed scan of a photograph would." If your only interest is in scanning your photographs, and you want the best looking images possible, go with the film scanner and scan your slides or negatives. There are some scanners that will do it all. If you want to scan mostly film and small prints the Hewlett-Packard PhotoSmart S20 scanner will scan 35mm slides or negatives and photos up to 5X7". This unit has a street price of under $200 and does a good job. See my full operational and features review of HP's S20 PhotoSmart scanner. The Epson Perfection 4990 Photo is a flatbed scanner that has a very capable transparency lid built in. Its 4800 dpi optical resolution makes it a reasonable choice for 35mm film scans. However the 4990 uses a fixed focus lens and a staggered CCD to achieve its 4800 dpi rating. For 35mm film scans it is not as good as a dedicated film scanner with a focusing lens. This scanner should do a very nice job with large format transparencies (4X5") and a good job with medium format films.
Most scanners use a CCD (charge coupled device) to capture the image that you are scanning. The CCD consists of a bunch of very small sensors that each respond to the colors, red, green or blue. This method of scanning using red, green and blue sensitive sensors is where the term RGB color comes from. While it is not quite this simple, for practical purposes these sensors are in a line in the optical path of the scanner. A scanner with resolution of 1200 dpi has 1200 sensors for each linear inch of the sensor. It can resolve detail at 1200 dots per inch in your image. Scanners that list their resolution at 1200X2400dpi achieve the 2400 dpi part of their resolution by mechanical means. This type of scanner will have 1200 sensors per linear inch but can move the scanning lamp and head or document at 2400 increments per inch. Scanners rated like this have an optical resolution of 1200 dpi and a 'mechanical' resolution of 2400 dpi. In this situation the 2400 dpi resolution is only really available in the motion direction of the media or scanning head. The scanner's software interpolates the sideways optical resolution to equal the 2400 dpi lengthwise mechanical resolution. When you see a scanner with this optical/mechanical resolution, you should really only consider the smaller number. The ability of the scan head or media to travel at the higher incremental resolution usually doesn't provide any more image quality than you would get from a resample (up-sizing) of that image in any decent imaging program. Many scanners advertise extremely high interpolated resolutions. Interpolated high resolution is just advertising hype. Scanning with these high interpolated resolutions will not provide you with high quality digital images. If you find that you do occasionally need images larger than your scanner's optical resolution can provide and you have a good mid grade imaging program, your imaging program will interpolate to larger size images as well or better than your scanner's software. Whenever possible scan and save images in 48 bit color depth (16 bits per color channel RGB). We will discuss the advantages of working with 48 bit color information a bit later.
DPI stands for Dots Per Inch and represents a user assigned/selected number of dots per linear inch on hard copy media. DPI is a standard used to scale media (film, prints or a document) to be scanned to a required pixel resolution. PPI, which is also user assigned/selected, stands for Pixels Per Inch and is used to scale the digital image's existing pixel dimensions into corresponding color dots on paper that make the required size print. Assigning a PPI number to an existing digital image creates a document or print resolution, also known as output resolution. In both types of scaling the dot size is variable with larger dots creating lower resolution and smaller dots creating higher resolution.
As an example, a 300 PPI photo print is higher resolution than 72 PPI because the dots in the 300 PPI print will be smaller and many more different colored dots will be used to make any particular object in the print. So, there will be more color shading information and detail in the 300 PPI print than the 72 PPI print. Changing the document resolution does not change the pixel resolution of the existing digital image. It only scales the existing pixels to a new print or document size on paper. You can ask your imaging program to resize (resize = resample - add or subtract pixels to grow or shrink the pixel resolution) and scale (assign a new document resolution) in one operation.
The terms DPI and PPI are relatively interchangeable. The term DPI is probably most appropriately used when you are scaling media like film or photos to be scanned to the required pixel dimensions. The term PPI is most appropriately used to scale existing digital images to a specified print size.
The math for scaling media to be scanned to a required pixel resolution or an existing digital image file to a required print size is not complicated once you grasp the concept. I'll provide some simple formulas below.
Formulas For Scaling DPI/PPI For Scanning Or Printing
In digital image creation and workflow pixel resolution (dimensions in pixels) is the first and most important decision. 'What pixel resolution do we need to print to 8X10 inches at 300 ppi output resolution?' -- ' What is the scanning dpi necessary to get 2400X3000 pixels from my 35mm film?' -- 'What pixel resolution does it take to fill up half my monitor display when it is running 1024X768 resolution?' We will adjust the DPI of the scanner or the resolution setting of the digital camera or resize the image in our editing program to scale the digital image to the pixel resolution that is required for a printing job or for our computer monitor display.
There are 4 related variables involved that can be arranged in simple math equations that will allow to you solve all of your digital image resolution and scaling requirements. The four variables are as follows: PIXEL RESOLUTION - DPI/PPI - ORIGINAL MEDIA SIZE - PRINTED OUTPUT SIZE.
Because computer screens are capable of running at different pixel screen resolutions (600X800 pixels, 1024X764 pixels and even higher) the image size on your computer screen is relative and is in direct ratio to the screen resolution of your computer. An image of 400X400 pixels on a screen running 600X800 pixel resolution will take up half of the computer screen's available side to side area. That same 400X400 pixel image on a screen running 1024X768 pixel resolution will take up a little more than a third of the side to side area of the computer screen.
In the Windows operating system there are basically two methods for scanning digital images. The first method uses your scanner and software to scan an image and then save that image file to a folder on your hard drive. You can then open that image file in the imaging program of your choice for further work. The second method available is done using a Windows driver called TWAIN. Believe it or not, the word TWAIN is not an acronym. TWAIN compliant scanners and imaging programs work together to allow you to scan directly into your imaging program. TWAIN compliant imaging programs have an 'import' or 'acquire' option under the file menu. They also have a feature to allow you to pick which TWAIN compliant scanner or digital camera you want to use to "acquire" your image. In TWAIN acquired images the software for that particular scanner or camera opens inside your imaging program and allows you to scan directly into that imaging program. There is no advantage to TWAIN scanning other than saving a little time when you are scanning just one image. See the official TWAIN web site for more information on TWAIN. - return to table of contents
Archiving Digital Images
In the recent past I saved most of my favorite scans as full resolution TIFF files. However, with the rapid improvements in film scanning technology I've found this practice to be a waste of time. Properly stored film will hold its color as long or longer than the life of most CDROM disks. 5 years from now, my scans may not be optimal quality anymore relative to the scanning technology available at that time. I am currently just scanning my images as needed for printing or digital image orders.
If you are using a digital camera or have a need to save and store digital images you will need to consider an appropriate, cost effective and reasonably simple way to save and catalog your images. A web search will turn up many software solutions for image collection management. My favorite all round image viewer ACDSee also has an image cataloging feature.
A CD writer is an economical method of saving, storing or transporting your images or image collection. A CD writer may be had for as little as $39. You can make a CD just for Windows or a universal CD that can be read in DOS, a Mac or a Windows computer. Good quality optical media is more stable than magnetic media. Magnetic media like ZIP disks shouldn't be trusted after 3 years. If you want to archive your image collection on CDROM you can save space on your CDs by saving as JPEG with low compression in the neighborhood of 1:3 and reduce the average file size over 60% from uncompressed TIFF files. Saving as full resolution gives you the most flexibility for future use of that image. To calculate image file size for uncompressed RGB images multiply the product of the resolution dimensions times three. As an example a 2700 dpi 35mm film scan will be about 3600X2400 pixels = 8,640,000 times 3 = 25,920,000 or 25.9 megabytes in 24 bit color. Multiply by 6 if you are saving 48 it color images.
If you are interested in archiving your high resolution image collection, DVD may be the most appropriate solution. Film scanners with resolutions of up to 4000 dpi produce image files in 48 bit color that range from 100 to 600 megabytes depending on film format. DVD disks can hold up to 4.7 gigabytes of data or nearly 9 gigabytes with the new dual layer DVD writers and disks. DVD writer technology is newer and a little more expensive then CDR technology with prices for DVD writers ranging from $69-300 and disk cost starting at about $.25. With the dropping prices of DVD writers and media, DVDR is probably the most efficient and cost effective way per megabyte for archiving digital image files. Be aware that very cheap DVD's have a shorter readable life span than low quality CDs If you intend to use DVD's for image storage I'd recommend doing some research on the archival qualities of the different brands of DVD. Here's a list I found of some of the best manufacturers of quality DVD's
1ST CLASS MEDIA
Digital Imaging for the Web or Email Using JPEG File Format
For web imaging and email attachments you have to work toward the best compromise in maximizing image quality and sharpness without creating large file sizes. JPEG is a lossey file format. That means that when you save an image as a JPEG some of the original pixel color information is lost. This isn't a bad idea when it comes to web imaging and email attachments. The computer screen is only about 72-90 dpi. You don't need the same amount of color information to make a nice screen image as you would to make a nice 8X10 print from a photographic quality digital printer.
When we talk about the amount of JPEG
compression we are talking about the amount of data loss during the JPEG file creation
process. The amount of compression is controlled by you through your graphics imaging
program. Compressing the image data helps to keep the file size down which makes the image
load faster in a web browser and download faster as an email attachment.
In a JPEG image color information is compressed
into 'blocks' of pixels using math algorithms that methodically blend all the
pixel colors in each block. Individual pixel color information is lost
permanently. Increasing the compression produces smaller computer file size is
in kilobytes or megabytes. Lower compression produces better quality but bigger
computer file sizes.
In a JPEG image color information is compressed
into 'blocks' of pixels using math algorithms that methodically blend all the
pixel colors in each block. Individual pixel color information is lost
permanently. Increasing the compression produces smaller computer file size is
in kilobytes or megabytes. Lower compression produces better quality but bigger
computer file sizes.
Graphical 'image optimizer' programs and program subroutines like Photoshop's "Image ready" allow you maximize web image viewing quality while keeping the image file size as small as possible. As you may have guessed by now, larger files sizes do not necessarily render better looking images. JPEG compression (file size) and the amount of image sharpening applied are two important considerations. See this page for some comparison examples of thumbnail image quality and JPEG compression.
Graphical image optimizers will also optimize GIF files by allowing you to select the number of colors in the GIF palette. You can optimize the GIF to blend into a particular background color if you already know the color of the background that you are setting the GIF in on a web page. GIF optimizers will also allow you to make the GIF image's background color transparent. I'll comment on a few different visual image optimizer programs a little later on.
Note: repeated editing of JPEG files will gradually degrade image quality. If you think you will need edit an image more than a couple of times, be sure to save a copy of the file in an uncompressed format like TIFF. Use this file for future editing and re-saving of that image to JPEG or other file formats. - return to table of contents
Thumbnail and Image Size Issues For the Web and Email
Thumbnail is a term commonly used to describe small images placed on a web page or sent as email attachments to friends and family. Naturally, bigger images will have larger file sizes and will be slower to open in a web browser and slower to download when used as an email attachment.
Thumbnail images of photographs should be big enough that the viewer can identify the content and get an idea of the overall quality of the image without having to download a larger version. I use 130X85 pixel sized thumbnails in my web photo gallery. Remember that computer monitors operate at different pixel resolutions. My web page's default thumbnails look big at 600X800 monitor resolution and they start to look small at resolutions above 1400X*.
My web thumbnail images are between 10 to 25k in file size. Many people are still on 56K dial up Internet access. I try to limit the total download for each web page to 250-500k or less. Most web developers agree that this data range of download per page is about all most people on dial up will tolerate. Accepting these parameters means limiting each of my pages to about 20 thumbnail images.
The larger versions of each of my web images that are available to download are about 750X500 pixels for the 35mm, 6X9cm and DSLR images and 600X800 for the 4X5 camera images. 35mm, DSLR and 6X9cm films don't have the same length to height ratio as a computer screen. Most web developers are currently designing sites to look their best at 600X800 pixel resolution. This is based on the assumption that most people are now using at least 600X800 pixel resolution or higher on their computer monitors.
If you want photos from 35mm scans to fill a computer screen that is running 600X800 resolution you'll need to size them to no larger than 750X500 pixels. If your viewer is running less than 600X800 screen resolution, they will have to scroll side to side to see the entire image. Another remedy for full screen presentation is to actually crop (cut) some off each side of the 35mm image until the image will resize to exactly 600X800. Files sizes for my larger images run between and 60 to 250k.
Seven years ago I picked 750X500 for my largest viewable web image because it was a compromise between working properly at 640X480 screen res and 600X800 screen res. Higher resolution images produce disproportionately larger files sizes. Very large images may cause long download times. If the download time becomes too long some folks will discontinue the image download. Also, web server storage and user account bandwidth allocations may become issues with large image files depending on how much disk space you are allowed to use on your ISP's web server and how much data download in megabytes you are allowed with your account. My photo web site uses nearly 150 megabytes of server hard drive space.
For email attachments the file size/download speed issue is still important because you don't want your family and friends to have to spend several minutes downloading your JPEG email attachment. There may be times when you will want to send an image that will nearly fill a computer screen. However, most of the time images in the 300X400 pixel size range will do nicely as email attachments. If you want to send two or three photos at one time, it is even more important to keep the file size of the images reasonably small. It is considered good Internet manners to ASK before you send any kind of image attachment to your friends or family. Some folks just don't want to spend time downloading pictures or they may just want to know when to expect the image download. - return to table of contents
Adjusting and Working with Digital Images
The following is the current routine I'm using for adjusting my scans using PHOTOSHOP CS2 and Windows XP. While the process may vary a little, the same imaging tools and procedures are available in any of the imaging programs that I have listed in the image editing software comments section above.
Digital image files from digital cameras seldom need much 'spotting' or touch up. Film and prints are sometimes damaged by handling or a lack of care during processing. Scans from damaged media will show every defect that was on the original.
The first thing I do to my scans is clean up the defects in the scan. Touching up digital images from scanned film or photos is far easier than hand spotting a photo print with fine brushes and pigments. The tools used in digital spot removal are very similar to actual brush and pigment but far more versatile. The most common tool is the clone tool (called the rubber stamp clone tool in some programs). the clone tool allows the user to select a predetermined pixel diameter area on the image to 'collect' pixels from that will later be pasted over the area to be touched up in the same diameter of coverage as the 'collection' area. The pixel collection area is usually very close or adjacent to the area to be 'repaired' or 'spotted'. The object is to find pixels that are nearly exactly the same color and tonal range as the scratched or spotted area and then replace the damaged area with the collected group of pixels.
The parameters for the clone tool are found in the tool properties bar that appears just under the top tool bar when the tool is selected. For a starting point select NORMAL for mode, 100% OPACITY and ALIGNED. Aligned means the selection point is always the same distance away from the placement point. If you uncheck aligned, the selection point stays at its original selection place on the image. To make a selection hold down ALT and left click the area you want to ‘collect’ the pixels from. Then place the cursor where you want to ‘place’ those pixels and do another left click. Every time thereafter that you left click the program will sample pixels from the pre-set collection area and place them in the area the cursor is over in the circumference area of the brush size. Brush size, shape and texture properties dialogs are available in the brush palate. You can do a quick brush size change by right clicking anywhere on the image and a size dialog window will pop up.
The second step in the image adjustment process would be to adjust the tonal range of the image using the RGB levels tool. I like to use the levels tool because it allows me to adjust the highlight, midtone and shadow areas independently of each other. Using a brightness or contrast tool shifts the whole tonal range of the image. Tonal values in an RGB image are assigned a number between 0 (for black) and 255 (for pure white). I'll provide a visual example of the process. Click the following link to see the original scan and histogram with no adjustments in the scanning software. Notice that the image is a bit flat and most of pixels are located on the darker side of the histogram. You can see that there are no very light or very dark pixels currently in this image. In the next screen capture of the Levels tool I've moved the left slider to the right and set the darkest area of the scan to value of zero (0). and moved the right slider in to set the brightest point of the scan to 255. I've also moved the middle slider a bit to the left to open up the midtones just a little. In this last screen capture you can see the final image and it's new histogram. Notice that there are now pixels ranging from 0 to 255 giving the image a broader tonal range and more contrast.
Some images look best when the sliders are moved exactly to the start of the graph on each end and some images look best when the sliders are moved close to the start of the histogram graph on each end. Setting the darkest areas of the image to digital 0 (actual black, by moving the left slider all the way to the start of the graph) will cause the darkest shadow areas in your image to lose some detail. The last part of the histogram adjustment is to move the middle slider to adjust the gamma or midtones of the image.
There are different types of levels histograms. You can actually adjust the tonal levels of each color channel independently of each other too. If your digital image is much too dark or way too light, you will notice that the image's initial histogram is way off to one side of the graph. This type of image may need to be re-scanned and adjusted with pre-scan tonal adjustments such that the tonal range of the image is somewhat balanced within the histogram graph. If your imaging program will handle 48 bit color, you should do all of your tonal range and color adjustments with 48 bit color files. Adjusting tonal range and color with 48 bit color files helps to keep the fine gradations in color information that were contained in your original 48 bit scan. After these adjustments have been made, you can convert to 24 bit color for any other image adjustments, manipulations or filter applications. I have an article called A Practical Guide to Interpreting RGB Histograms that provides detailed information about histograms and the levels tool.
You can also adjust tonal range with a curves graph if you have that tool available in your imaging program. Adjusting curves to achieve the correct tonal balance is a little more complicated then levels but allows even more control than a levels adjustment. Using the curves graph you can move any given portion of the tone curve (0-255) independently of the rest of the curve.
The manipulations I've described work well for me using Photoshop. I suggest that you check out the tools available in your imaging program and do a little studying. Learning by experimentation works well for many people too since you can't ruin "digital film" as long as you don't save your early attempts over your original digital file. After you have made your adjustments do a 'save as' and name the new file something similar to the original file. Doing a 'save as' preserves your original digital file. After I've adjusted tonal range I'll fine tune color using the color balance tool. Occasionally I'll use the hue and saturation tool. Color correction is pretty much a visual operation but you can use the color picker and info palate to check your RGB color numbers against what you 'think' you are seeing. As an example, you have an area that should be pure white. You can put the color picker or cursor over the white area and read the current color values as 230r, 230g and 240b indicating that you have a slight blue cast to your image. Adding a little yellow with the color balance tool will remove the blue cast or lowering saturation of the blue channel in the hue and saturation tool should accomplish a similar result.
You can also correct color casts and set white and black points with the color pickers in the levels adjustment tool. It has a picker for pure black, neutral gray and white. The white and black pickers in the levels adjustment shift the 'clicked on' pixels to 0 or 255 depending on which picker you selected and then shift the rest of the image's pixels appropriately. The midtone picker in the levels adjustment is the same as a 'white balance' although it uses neutral gray to accomplish neutral color. If you use this approach, make sure the area you click on should actually be pure white, pure black or neutral gray. In fact, most images have very little, if any, areas that should be 0 or 255 on all channels. There is no visible image detail in 0 or 255 on all three color channels. As a general rule you can consider color numbers in the 20's to 30's the low end of noticeable shadow detail and color numbers in 240 range as the high end of viewable highlight detail.
After tonal range and color have been adjusted I usually apply the unsharp mask filter. Unsharp mask has three different adjustable parameters to adjust image sharpness. The recommended settings for these adjustable parameters are different depending on the resolution (size) of the image. Unsharp mask is actually an adjustable edge-sharpening filter. Unsharp mask increases the contrast between the edges of different colors. The 'amount' setting controls the strength of the filter. The 'radius' setting controls how many pixels in from the color edge are affected. You will usually need larger radius numbers for larger images. The 'threshold' option controls how different the colors on opposing sides of an edge have to be before the filter applies itself to that area.
I usually set the amount parameter between 60 and 90. I use a radius between of .4 or .5 for thumbnails and .6 to .8 for images of 750X500 pixels. I may use a radius of up to 1.5 to 3 for images of 2000X3000 pixels and above. I use a threshold of 2 or 3 for most images. Using plain sharpen filters will make the smooth mid tones in your image look a bit grainy. You will want to experiment a bit to get the effect you are looking for. The visual effects of the unsharp mask filter may be lessened when you resize an image that has previously had this filter applied. Since different size images require different amounts of this filter to look similarly sharp, you MAY need to re-apply unsharp mask with appropriate filter parameters after resizing an image. In my opinion there is nothing worse looking than an overly "sharpened" image. Use this and other sharpening filters with care.
You can find a more detailed explanation of histogram and curves tools and information on how to use these and other imaging tools to improve your scans in my Practical Guide to Interpreting RGB Histograms article and the "Scanning 101 - The Basics" section of Wayne Fulton's Scantips web site.
At this point we need to consider what use we have planned for the image. If it is for printing, we will leave it at it's highest resolution. if it is for the web, computer slide show or email use, it's time to resize (reduce the resolution) the image.
Resizing and resampling basically mean the same thing. If you size down an existing digital image you are 'resampling' it to a smaller pixel dimension, which is the same thing as lowering the pixel or image resolution. Your image manipulation program is re-sampling (checking) the existing pixels and subtracting pixels in an orderly fashion to make the image smaller. You can also resample an image to a larger pixel dimension. In this case the program looks at the image, interpolates the existing pixel data and adds similar pixels next to each existing pixel. Resampling an existing image to a larger size (higher resolution) will always cause some image quality loss because the imaging program has to make 'educated guesses' on the color for the pixels it is adding. Resampling to a smaller size will not cause noticeable image quality loss. Naturally, once an image has been sized down, it cannot be sized back up again without some quality loss. Always save a copy of an image at the highest resolution you think you will ever need. When you are resampling an image, use bicubic interpolation if you can select your interpolation method. Bicubic produces the best image quality. Some programs may not allow you to chose the interpolation method.
For computer screen images the pixel size of the image (pixel resolution) is the only thing to concern yourself with. For computer screen images you are only using dpi in your scanning process to scale your digital image to the exact pixel size you want to display on your computer screen.
If you are using a digital camera, you will almost always have the option of taking the picture in high, medium or low resolution to start with. I'll repeat the information I gave in the Scanning Basics heading but with a slightly different approach. let's say you have a 4X6 inch print you want to scan and you want your scanned image to cover about one half of your computer screen's side to side area. If your computer screen is running 600X800 pixel screen resolution, you'll need an image about 400 pixels wide to cover one half of your screen's side to side area. Using the formula I listed in the scanning basic section (Desired pixel size divided by the original media's dimensions (in inches) = scanning dpi. The width of our original media is 6 and the desired pixel size is 400. 400 divided by 6 = 66.6. We'll need to scan our 4X6 print at about 67 dpi in order to get a 400 pixel wide image. We will cover scaling for printed output in the Resampling, Scaling, Printing and Dpi section.
If I am intending the image to be an email attachment, I'll decide (approximately - since I don't necessarily know what computer screen resolution the image will be viewed at) how much of the screen I want the image to cover when it is viewed by the recipient and then resize the image accordingly. If I intend to put the image on my web site, I'll first resize it to my larger downloadable web image size. After this first resizing I'll apply the unsharp mask filter. In Photoshop if your default working space is anything but sRGB, you should convert the profile to sRGB before saving for web. This insures that the image retains the same visual color characteristics you saw in Photoshop when later viewed on the web, email or image viewing program. The next step is to do a 'save for web' using Photoshop's Image Ready program and give the image a recognizable name and save as JPEG file format. To make the web thumbnail all I have to do is resize the image again to my required thumbnail size. At this point I may re-apply unsharp mask. In some cases the visual effect of the previously applied unsharp mask filter may become lessened during the interpolation and resizing of the image to the smaller version.
The last step in preparing my web image set is to do a 'save for web' for the new thumbnail size image using Photoshop's Image Ready. I'll use the same name for the thumbnail as I used for the larger image with the exception of adding '-sml' to the end of the thumbnail image name. By adding '-sml' or 'thmb' to the thumbnail's name it's always easy to see which thumbnails belong to each larger image. Read more details about the unsharp mask filter and saving web images in the next three paragraphs
Saving your web or email images using a visual graphics optimizer like Photoshop's Image Ready, Photo Impact's web image optimizer or Pegasus Imaging's JPEG Wizard allows you to visually preview your image's quality and it's file size before you save it. You can change the amount of JPEG compression and re-preview the image until you have just enough JPEG compression to make sure the image looks nice. While you are compressing and checking image quality you can also keep an eye on the file size to insure that the image will still download reasonably fast.
JPEG Wizard's main claim to fame is that it doesn't decompress your existing JPEG files when it opens them. This feature effectively removes the problem of incremental quality loss upon each re-opening of a JPEG file. JPEG Wizard has many sophisticated user selectable options and parameters for editing, sizing and saving JPEG files. One of the options in JPEG Wizard is the ability to remove extraneous file information that may be embedded in the image file by your digital camera or graphics program. This embedded information may be useful when the image is opened in an imaging program but it is just wasted file space that increases download time if you are intending the image for web placement. JPEG wizard also allows regional compression settings and a host of other nifty options. JPEG Wizard, PhotoImpact's web image optimizer and Image Ready are always opened and used after all of your image manipulations are complete.
Some general guidelines for web image file size would be to limit large downloadable web images to between 60 to 200k in file size and web thumbnails to between 10 to 25k in file size. - return to table of contents
All the same skills necessary for web/computer screen imaging will translate to desktop photo printing too. There are just a few differences. Printing from any of the graphics programs mentioned on this page is very simple. The main difference between imaging for the web or computer screen and imaging for output as a photo print is the file size and type. You will want to scan and save full resolution digital images as TIFF files. TIFF is an uncompressed file format. Color space and ICC profile information can be 'imbedded' in a TIFF file. You can also get very nice prints from high resolution low compression JPEG files, which also support imbedded color or profile information.
Scaling digital files for printing is a process that seems to cause some confusion for people who are at the beginning stages of learning to work with digital images. After a digital image is created the ppi number assigned to that image is only used for scaling printed output size. Using Photoshop's image size dialogue box as an example, if you uncheck resampling and change the ppi (resolution in pixels per inch) setting, you'll notice that you are only changing the printed output size of the image and not the pixel dimensions or resolution of the image. Since dpi / ppi and pixel resolution are in direct ratio to each other, you can change the resolution (pixel dimension size) or ppi setting of your existing digital image to achieve your goals. In summary, changing the assigned ppi of an EXISTING digital image only changes (scales) the printed image size. Resampling/resizing changes the actual pixel dimensions (pixel resolution) of your digital image.
I'll give one more example to help clarify the differences between an image's pixel size, dpi and printed image size. Scanning a print, slide or negative at a certain dpi will render a digital image with pixel dimensions (height and width in pixels) in a direct ratio to the size of the original image (height and width in inches). I usually scan my slides at my scanner's full resolution of 4000 dpi. This produces a digital image of about 3650 pixels in height by 5500 pixels in width and gives me the maximum flexibility for later uses of the digital image. This dimension is achieved by taking the approximate dimensions of the actual photo area of the slide or negative (.91 by 1.37 inches) and multiplying them times the dpi selected for the scan (.91 times 4000 = about 3650 and 1.37 times 4000 = about 5500. If I want to print that digital image, I'll have to scale it to the printed size I want. We will now assign a dpi setting to the scanned image in order to scale the image for printing. If I used the same dpi setting to print (4000) that I used to scan, I'd get an image exactly the size of my original slide or negative at .91 by 1.37 inches. Let's say I want to print at 300 ppi to 8X10 inches. As mentioned earlier, printing at 300 ppi is universally accepted as the standard starting point for digital quality photographic output. I'll need to resample the image down to a smaller resolution in order to achieve this size print when I assign 300 ppi as the document's printing resolution. I'll also need to digitally crop the image from the 35mm film's 8X12 native ratio to 8X10. We can crop the image and resample it to a resolution that will print to 8X10 at 300 ppi in the same digital manipulation by using the crop tool in Photoshop. In the crop tool's options we'll select 8 inches as the 'height', 10 inches as the 'width' and 300 as the 'resolution'. We then start the crop at either upper corner of the image and drag the cursor toward the opposite bottom corner of the image. Photoshop will 'constrain' the crop area to the proper 8X10 ratio. We then drag the entire crop selection box around in the image and place it such that it contains the area of the image we want in our final print. When we execute the crop, Photoshop will crop away the unwanted part of the image and resample (resize) the part of the image we selected to the proper pixel resolution of 2400X3000 pixel resolution. Other imaging programs may not allow you to crop and resample at the same time. You'll have to look at your imaging program's help menu under 'crop' or 'sizing' to see if you can do both operations concurrently. For a review of the math involved in these examples see the Formulas section above.
If you try to print an existing digital image at ppi settings lower than 200 ppi you may notice some quality loss in the print. As an example, you have a 2400X3000 digital image that will print nicely at 300 ppi to 8X10". You decide to print that file at 16X20". Using our formula #4 you find that you will have to print it at 150 ppi which will yield a less than photo quality print. You could resample the image to a higher resolution in your imaging program but the necessary up sizing interpolation would also decrease the quality of your image a little as the program has to make 'educated guesses' and add pixels throughout your image to increase the pixel dimension of the image. The pixel subtraction interpolation necessary to resample an image to a smaller resolution generally don't decrease the visual quality of a digital image at all.
When I say printing at the equivalent of 300 ppi for photo output is standard, I probably need to do some qualifying. The human eye sees 300 ppi output at normal viewing distances as continuous tone. Of course, this assumes output from a photo quality printer which has a decent dot layering process. If you own a photo printer and its native printing resolution is 720 dpi, the printer’s driver will resample (interpolate) any file you send it to print at its own native resolution using the PRINT SIZE information that was sent from the program you are printing from. The point I’m trying to make with 300 ppi is that if you have a capable photo printer and enough pixels to print to the size you want at 300 ppi, you should get photo realistic continuous tone looking images regardless of your photo printers native printing resolution. I’m not saying that you might not see slightly better prints if you send your 1440X720 dpi Epson printer a file for an 8X10 print that is 5760X7200 pixels (for 720 ppi output) instead of 2400X3000 (300 ppi output). Before you make a habit of sending huge files to your printer, do some comparative testing to see if you get much, if any, improvement from the higher resolution files. - return to table of contents
Enlargement Size vs. Resolution Issues
scanners that have optical resolutions in the 2400 to 2700 dpi range have just enough resolution for making photo quality (300 ppi) prints up to 8X12
inches. In order to print to 11X14 at photo quality you'll need
to scan 35mm film at about 4000 dpi. As we saw in the paragraph above, 8X12 is the largest size print available at photo quality
(printed at 300 ppi) from a 2700 dpi 35mm film scan. If you have a 2400-2700 dpi
film scanner or a 3 - 6 megapixel digital camera and you want to make larger prints,
I recommend resampling the image to larger and appropriate pixel dimension
(resolution) in a capable imaging program before you send the image file to your
In my opinion, images from high end Digital SLRs can be resized up to a greater percentage of original size than film or print scans or point and shoot digital camera output. This is because there is no film grain and very little digital noise in images from DSLR cameras. Film grain and noise artifacts tend to get magnified in resized film and print scans and become more noticeable in an image that has been resized to a higher resolution. Also, output from a DSLR is a first generation image while a film scan is a second generation image (film to digital image) and a print scan is a third generation image (film to print to digital image). Some image quality loss occurs at each stage of processing in the film to scan or film to print to scan workflow.
Many people do print 2700 dpi 35mm film scans or even resampled 3.3 megapixel camera images to 11X14 and beyond and are happy with the results. However a person with a discriminating eye MAY notice a loss of sharpness in 11X14 and larger prints when printed from files that would have had an original resolution requiring 150 ppi to print to 11X14. On a personal level 'photo quality' is a subjective judgment. On a professional level, hardly anybody accepts less than 300 ppi for photographic output. Almost all of the high end professional digital printing devices like LightJet, and the Fuji Frontier system make the best quality prints with files that have enough resolution to print to the desired size at 300 ppi. As mentioned above, resize and scale your digital files to the appropriate dimensions in an imaging program instead of letting your printer driver size and scale the digital image. - return to table of contents
Photo Quality Printers
There are a limited number of printers designed for the consumer market that will produce true photographic quality images. Hewlett-Packard's PhotoSmart printers, Epson's Stylus Photo models and the Canon PIXMA series and i9900 printers are photographic quality inkjet printers. If you are interested in a home digital darkroom, be sure to do adequate research. You'll need know which printers of any given brand name are designed to produce true "photographic" quality continuous tone looking prints. Photo printers have widely varying specifications and capabilities. Some even have a few well known shortcomings that may be of particular interest depending on your intended application. If you expect your prints to last without any fading beyond a few years, you should consider Epson's 2200 or R1800 (13" wide paper) or R800 (8.5" wide paper) printers. These printers use pigmented inks that are rated to a 60 year life or more. Hewlett-Packard's latest Photosmart series printers have dye based inks that are also rated in the 60 year life range. At this point in time I'm not ready to trust dye based inks for archival prints no matter what fade free life time the manufacturer may claim. I recommend spending some time reading and posting questions to the Usenet news groups rec.photo.digital, comp.periphs.scanners and comp.periphs.printers (See Google's Groups) before you start investing in your digital darkroom. You can also read my comments on the photo printers that I have used during the last 7 years. - return to table of contents
Some Image Editing Tips For Photoshop
The following tips are for Photoshop users. They may be usable with some modifications with other mid range to high end digital imaging programs too. The explanations and directions given for these tips assume that you know how to use the tools available in Photoshop and have a basic understanding of some of Photoshop's more advanced features like layers.
Burning and Dodging: Photoshop actually has burn and dodge tools available in the main tool box. The dodge tool looks like the magnification tool except it is black. The burn tool looks like a hand with the fingers together. For those of you who have never worked in a darkroom burning and dodging is a method for selectively darkening or lightening an area of your image. Select the dodge tool to lighten an area and the burn tool to darken an area. Pick a brush size appropriate for the area you want to darken or lighten. I suggest using a brush size that is almost as large as the area you want to alter. In most cases you'll want to use a 'soft edged' brush. Technique is important but you can 'undo' or delete 'history state' until you get it just right. The following image link is a two image before and after using the dodge tool. The original photograph is from my 4X5 camera and 90mm lens. The 90mm lens has significant light fall off in the corners and to a lesser degree around the edges. In other words it has somewhat of a central hotspot. I used the dodge tool to lighten up the dark corners and applied just a little bit of dodging around the bottom edge.
Using The Linear Gradient Tool For Correcting Light Falloff In The Corners Of Your Photos: For Photoshop CS and earlier versions. Photoshop CS2 has a new vignette tool that takes care of this issue very nicely.
Photoshop CS, 6 or 7 make a new layer in overlay blend mode. Choose the 'gradient' tool from the left main toolbox. Pick the 'linear' gradient tool from the gradient tool property bar selections (rectangular box fading from light to dark). In the gradient tool's properties bar set mode for 'normal' and 'opacity' between 20 and 40%. You'll need to experiment with this parameter. Make sure the 'transparency' and 'dither' boxes are checked. Open the gradient editor by clicking on the sample gradient in the gradient tool's property bar. Select the 'foreground to transparent' gradient (Upper left corner of icon starts with gray and blends to checkered in lower right corner). Select 'solid' as the gradient type and 100% in the 'smoothness' box. Double click the bottom left color stop in the gradient editor and set all color channels to 255. Double click the bottom right color stop and set all channels to 175. Click the upper left 'opacity' stop in the gradient editor and set the opacity to 50%. Enter a name for your new gradient where it now says 'custom' and click on 'new' in the gradient editor to save this new gradient. Use this new gradient for all your parameter experiments. See a screen shot of the gradient editor by clicking here. Make sure the new layer is selected and put your cursor in each corner of the image and click and drag toward the diagonal corner about 30 to 40% toward the middle of the image (upper left corner toward lower right corner - etc). This will lighten up the corners. Experiment with the amount of opacity and the length of your dragged line. You can also experiment with the angle of the dragged line. The projected image circle of a lens is perfectly round but the image area is rectangular so the light falloff may not be exactly centered in each corner. Dragging the line closer to one side of the image will warp the gradient out further on the opposite side of that particular corner. If you find you have noticeable banding in the area you lightened up, add 5-10% of noise filter (filter/noise/add noise/uniform) to the overlay layer.
Photoshop CS will allow you to use the gradient tool in 16 bit mode. You shouldn't need to add a layer if you can work in 16 bit mode because there should be no banding or posterization in 16 bit mode and no need for the selective (in layer) application of the noise filter.
You may need to follow up the application of the gradient with a small amount of very selective dodging in the corners. If you find you need to bring up some dark 'accent' colors in the corners, set the dodge tool to 'shadows'. Experimentation and technique is the key to success with this process. The parameters I've listed are reasonable starting points. You want to approach this type of manipulation carefully. Large amounts of correction will make the image look unreal. If you are having problems, try multiple applications for each corner with 10-15% opacity.
See an example of this technique below. Move your mouse on and off the image to see the before and after. Notice that the central hotspot is reduced in the image that has had this manipulation applied to it. This photo of a sand wash was taken in Anza Borrego Desert State Park with a Rodenstock 65mm Grandagon N lens with a circular polarizer on 4X5 Velvia. The new Photoshop CS 'color replace' brush was used in the lower left and right corners to bring the colors back to their original hue.
Using Layers And Color Range To Control Color Density: There are times when you want to adjust the density of some specific parts of an image and burning and dodging will not work because of the size and shape of the areas you want to manipulate. Photoshop has a feature called color range which will select pixels in a particular color and tonal range using the eye dropper tool within the 'select color range' tool dialog. Open the 'color range' tool by clicking select/color range from the upper toolbar. This brings up the 'color range' dialog. I use the 'image' view option and pick the standard eyedropper. Click the eye dropper on the area you want to modify. Switch to the 'selection' view and use the 'fuzziness' slider to adjust the range of color in the area you want to modify. At this time you can choose to 'feather' your selection a little by going back to select/feather and setting a number between 1 and 5 pixels. The more feathering you do, the less sharpness you will have in sharp edged subjects. I have found little advantage to feathering. Now make a new layer by going to layer/new/layer via copy. Now you have some decisions to make. I personally prefer 'normal' for the layer option and 100% for opacity and then adjust tonality for each new layer by using the 'levels' tool. This seems to give me the most flexibility in adjusting the tonal range of my new layer selected area. You can also use 'multiply' for the layer option and use the opacity slider to control density. Once you select 'multiply' the new selection area darkens up and you adjust the tonal range back down using the opacity percentage. In this 2 image comparison example image of a desert view and skyline I choose the washed out light area of the sky just above the horizon for my first 'color range' selection and then did another 'color range' selection for the darkest areas of the hills in the foreground. This gives me three layers including both new selections and a background layer that contains all of the original image information. I wanted to open up the shadows in the hills and just barely darken the sky just over the horizon. The differences between these two images are subtle and this is just an example I picked out of a hat. However, I'm sure you'll get the idea after some experimentation. As with any digital image manipulation, small amounts of adjustment will usually help your image without introducing unnatural looking effects. Using large amounts of adjustment with the levels tool will introduce noticeable color shifts. When you are satisfied with your image you can save it as a Photoshop (PSD) file or go to layer/flatten image and save it in any appropriate file format.
Touch Up And Spot Removal With The Clone Tool: Film and prints are sometimes damaged by handling or a lack of care during processing. Scans from damaged media will show every defect that was on the original. Touching up digital images from scanned film or photos is far easier than hand spotting a photo print with fine brushes and pigments. The tools used in digital spot removal are very similar to actual brush and pigment but far more versatile. The most common tool is the clone tool (called the rubber stamp tool in some programs). the clone tool allows the user to select a predetermined pixel diameter area on the image to 'collect' pixels from that will later be pasted over the area to be touched up in the same diameter of coverage as the 'collection' area. The pixel collection area is usually very close or adjacent to the area to be 'repaired' or 'spotted'. The object is to find pixels that are nearly exactly the same color and tonal range of the scratched or spotted area and then replace the damaged area with the collected group of pixels.
The adjustable parameters for the clone tool are found in the tool specific tool bar that appears under the ‘file/edit/image toolbar at the top of Photoshop's user interface after the tool is selected. For a starting point select NORMAL for mode, 100% OPACITY and ALIGNED. Aligned means the selection point is always the same distance away from the placement point. If you uncheck aligned, the selection point stays at its original selection place on the image. To make a selection hold down ALT and left click the area you want to ‘collect’ the pixels from. Then place the cursor where you want to ‘place’ those pixels and do another left click. Every time thereafter that you left click the program will sample pixels from the adjacent collection area and place them in the area the cursor is over in the circumference area of the brush size. A right click will bring up the brush properties dialog and you can move the slider to produce an appropriate sized brush. You can set a variety of other parameters such as the 'hardness/softness' of the brush by accessing the 'Brush' toolbox.
Occasionally one may find use for a 'paint' brush tool in touch up work. The difference between the clone tool and the paint brush tool is that the paint brush uses a user selected color from the program's available colors palette. Most digital image spot removal and touch up is done with a clone or rubber stamp tool because the solid even toned colors that are applied with a paint brush tool are seldom seen in photographs. - return to table of contents
PHOTOGRAPHY AND DIGITAL IMAGING INFORMATION
Basic Digital Imaging Terminology FAQ*
COMPUTER SCREEN RESOLUTION: Computer screens are capable of displaying different amounts of pixels across their length and height. As an example a low resolution monitor setting may show a maximum of 1024 pixels in the width of the screen by 768 pixels in the height of the screen for a total of 786,432 pixels. A higher resolution monitor setting may allow you to show 1280 by 1024 pixels or more on your computer monitor. Using a little math you can see that when computer monitors of the same size are running different resolutions, the pixels on the monitor that is running low resolution will be larger than when that same size monitor is running high resolution. High resolution settings on computer monitors contain more graphical information but that information is in a smaller viewable format. See a screen capture image of Window 98's screen settings dialogue window.
CMYK COLOR: Stands for the subtractive colors of CYAN, MAGENTA, YELLOW AND BLACK. These are the component colors generally used in almost all printing processes. These colors blended in various combinations produce all the colors of the rainbow on printed material. They are called subtractive because the dyes in the inks only reflect certain colors, thus they 'subtract' the other colors of the rainbow.
COLOR SPACE: Denotes a calibrated standard for any given range of colors. sRGB and Adobe RGB 1998 are both calibrated color spaces. Adobe RGB has a wider color gamut then sRGB. Calibrated in this instance means that there are accepted assigned values for the range of colors within a given color space.
COLOR GAMUT: The range of colors within a calibrated color space. Some color spaces are 'wider' than others in that they contain more variations of colors.
CROP OR CROPPING: Using the selection tool or crop tool of your image manipulation program to draw a box around a selected portion of your digital image. When you execute the crop your remaining picture contains only what was inside your drawn box. See a screen capture image of a crop tool that is about to be applied to an image.
CURVES: The same basic adjustments as found in the levels/histogram tool. A curves tool starts with a straight diagonal line graph representing the tonal range values from 0 through 255 (black through pure white). The curves tool usually allows you to set an indefinite number of points on the line. Using these points you can 'bend' the line to adjust the image's tonal range at any point in the 0 - 255 graph. This type of tool is usually only found in intermediate to advanced image editing programs. See a screen capture image of a curves tool.
DIGITAL IMAGE: Denotes any computer file format that contains a graphical image instead of text or program data. Photographs and documents that have been scanned and digital camera photos end up as digital image files. Digital images can also be made from scratch in a 'draw' or 'paint' program. There are basically two types of digital images. A 'bitmapped' image contains information for placement of each and every pixel in the image. JPEG, GIF, TIFF and BMP are probably the most common type bitmapped digital image. JPEG, GIF and TIFF are readable in both PC and Mac format computers. All digital cameras and scanners produce bitmapped digital images. Most 'Paint' programs also produce bitmapped digital images. The other type of digital image is called a vector based image. Vector images map the outlines of an image and fill in the areas inside the mapped areas with color. This is the kind of image produced in 'draw' and 'illustration' programs like Adobe Illustrator and Corel Draw. These file types are most often proprietary to the program that creates them as they are not usually displayable outside of the program that created them until they are converted into a bitmapped image.
DOCUMENT RESOLUTION: Also known as OUTPUT RESOLUTION. A user assignable/selectable number in pixels per inch PPI that scales the pixel dimensions of an existing digital image to a required print size. Imaging programs, scanners or digital cameras may embed a 'default' document resolution number in the digital image file information header. You can change the document resolution number of the digital image in your image editing program to create any required print size.
DPI: Stands for 'dots per inch'. DPI always represent dots per linear inch on media. It can be used to denote how many dots per inch are used to produce a printed page or DPI can be used to scale a document for scanning to a required resolution ( pixel dimensions). As an example if you scan a 4X6 photograph at 150 dpi, the resulting digital image will be 600 pixels wide by 900 pixels long. The math as follows: 4 inches times 150 dpi = 600 and 6 inches times 150 dpi = 900. Using the math in reverse with our 600 by 900 pixel image and printing it at 150 dpi gets us back to our original 4X6 inch print size.
GAMMA: In a nutshell, computer monitor brightness and contrast
GRAPHICS PROGRAM: Also known as an image manipulation program, imaging program etc. Any computer program that can alter or create digital image files. A few of the best known as follows: Adobe Photoshop, Adobe's Photoshop Elements, Paint Shop Pro, and PhotoImpact
HISTOGRAM: A graphical representation of the tonal range levels from black to pure white (0 = white - 255= black) that are contained in a digital image. See a screen capture image of a histogram of an image that was opened in Photoshop.
ICC PROFILE: A computer file that can be used by your imaging program to provide the information necessary to convert color data between native device color spaces (the color numbers generated by your scanner, camera's CCD or imaging program) and device independent color spaces (the exact ink colors of a particular brand and model of printer). See more information on the ICC approach to color management by visiting the International Color Consortium's web page. Privately made ICC profile files can be found on the web. See the Inkjet Mall for ICC profiles for many of Epson's photo printers. Many printer and scanner manufacturers are making ICC profiles available for their products. You can also purchase software that will allow you to make your own ICC profiles, see Monaco Systems. High end scanners frequently come with calibration routines that allow you to make an ICC profile for that particular scanner.
INTERPOLATION: Most commonly associated with sizing or resizing a digital image. When you resize a digital image the imaging program 'resamples' the digital data and interpolates the data in order to determine how and where to add or subtract pixels to make the image smaller or larger. In simpler terms interpolation means that the imaging or scanning program looks at the existing pixel map of the image and adds or subtracts pixels in an orderly fashion to increase or decrease the resolution (pixel dimensions) of your digital image.
LEVELS: Usually refers to an imaging tool that usually combines a histogram graph and 3 sliders that allows you to adjust the tonal ranges of your image. The three adjustable areas are blacks, mid tones (gamma) and whites. This type of tool is usually only found in intermediate to advanced image editing programs. See a screen capture image of Photoshop's levels tool
PPI: Stands for 'pixels per inch'. PPI is used to scale a digital image's pixel dimensions to a physical dimension on printed media. Best use of the terms DPI and PPI as follows; Use the term DPI for scaling original media for scanning and use PPI for scaling digital images for printing. The math for scaling image resolution or print output is the same regardless of application or terminology.
PIXELS: A unit of measurement for resolution or size of a digital image. Each pixel represents one DOT in a continuous matrix of dots. This matrix of dots, when viewed on a computer screen, make up the content of your digital image. Each pixel has a computer word that contains information for the color of that pixel. Actual pixel size is relative to the resolution you are using on your computer screen. See the computer screen resolution heading for an explanation of the variable display size of pixels.
RESIZING AND RESAMPLING: Both of these terms refer the same image manipulation. When you resize or resample you are specifying a new pixel dimension for your existing digital image. This action is also known as changing the resolution of your digital image. See a screen capture image of the 'image size dialogue box' from an image opened in Photoshop.
RESOLUTION: The actual pixel dimensions of your digital image in length and width. As an example, an image that is 200 pixels tall by 300 pixels wide would have a resolution of 200X300 pixels.
RGB COLOR: Stands for the additive colors of RED, GREEN and BLUE. These are the component colors that are used in capturing images or displaying colors on all digital cameras, scanners and computer screens. These colors in various combinations can produce all the colors of the rainbow, so to speak. In a nut shell, these are the basic component colors of all visible light.
SCALING: This term refers to changing the printed size of your digital image or choosing the resolution for a digital image you are about to scan or create. Print size (PPI) and image resolution (in pixel dimensions) are totally independent from each other. However, as shown in the previous heading, the ratio between pixel resolution and assigned PPI is what determines the printed size of your photograph. Most digital image file formats can save print size information. This is done by embedding a user or program selected PPI setting in the digital file. See the DPI heading above for more information. See a screen capture image of the 'image size dialogue box' from an image opened in Photoshop. - return to table of contents
PHOTOGRAPHY AND DIGITAL IMAGING INFORMATION
Beginners Level Digital Darkroom Slide Show Tutorial
Digital Darkroom Imaging and Printing Tech Tips
Photography Tech Tips
A Practical Guide to Interpreting RGB Histograms
Digital Camera Raw Converter Comparisons
Digital SLR vs. Film Scans
DSLR Sensor Size and Pixel Density
Aftermarket Scanner Control Software
My Photo Equipment
Building Your First Web Site Mini Tutorial