All content copyright 2002-2005 Michael Papet. All rights reserved.
Just enough stuff to make sure you are getting the most out of your computerized darkroom.
Color management attempts to makes sense of mathematical values that are translated into colors. 255.255.255 doesn't automatically render an RGB "white." In a color managed working environment, the color white is rendered with hints provided by color profiles. Even with the hints provided, the color "white" (255.255.255)changes dramatically from monitor, to printer, to another monitor. The technical term is device dependent color. It is very important to understand that color management attempts to improve color accuracy without actually knowing what colors look like. Not a clue. It's good guessing mixed with a great deal of psychology/biology.
Calibration: Get your computer hardware into a "known state." In this case it means making sure Red Green and Blue values are being rendered correctly by the scanner, monitor and printer.
Characterization: More commonly known as "profiling." The correct term is characterization. Establishing the color characteristics of a particular device.
ICC Profile: The standard by which devices are characterized. Windows and Mac have different extensions as well as handle color profiles differently, but they rely on the same programming standard.
Gamma: A set of values that are applied to an image that when graphed, resemble a curve. Gamma is applied to boost color contrast for display devices like monitors and printers. My understanding is your eye tends to recognize colors in a non-linear way and gamma is the way to best exploit this.
sRGB: An especially limited color space preferred by HP, Microsoft and others. The more demanding user will have a better experience if they choose a different working color space in which to capture, edit and print images. For the web, it works okay.
Your scanner, monitor and printer should each be calibrated before being characterized. Other than Lasersoft's Silverfast, I'm not aware of scanning software that calibrates the scanner. Your monitor's blackpoint and whitepoint are probably not set correctly either. Again, calibration should be done before running a monitor characterizing application like Adobe's Gamma Utility. In both cases, the devices should be warmed up before attempting calibration or characterization. Printers for the most part, aren't calibrated.
Now that your devices are calibrated, go ahead and invest in characterization software. GretagMacbeth and X-rite are the two most well-known in this field. ITEC and Waytech are two others doing good work. Their solutions generate custom ICC profiles and in more expensive packages, they have their own color management engine.
Beware packages that use your scanner to generate printer profiles. Nearly all flatbed scanners simply are not precise enough to record color swatches from a printed target. If you choose this route, seek freeware profiling software to do the job. Without investing in proper measurement tools, scanning a printer target may give unexpected results.
Color management for personal computers attempts to solve the very difficult problem of creating a consistent color experience across many media types.
It does this by embedding a small file that describes a couple of color spaces. In really great graphics applications, color spaces have either been custom-selected by yourself or in better applications embedded by the software developer. The color spaces have vital information about white point, black point and color gamut information.
In better imaging applications the color management module can adjust the color for each purpose. For many users, the results are excellent. Photoshop has excellent color management implementation. Some imaging applications have little or no color management. Canon's scanner driver is a good example of an application with no color management.
To minimize your color issues, I have the following free advice:
In no particular order:
Epson's and Canon's color systems are not ICC compliant. For Windows users, I'm uncertain how this affects color rendering as Microsoft obligates you to use sRGB if no profile is present. In Canon and Epson's systems, will Microsoft recognize their proprietary profile? It's a good reason to buy SilverFast.
Since Microsoft's treatment of color management policy is so hard to explain as well as predict, the best advice I can offer is make sure each device has a profile associated with it.
Both Windows and Mac user's need to establish what the gamma setting for the monitor and graphics card is before using Adobe's Gamma Utility. It is an unknown in many instances.
Because RGB color is device dependent and open to all kinds of manipulation that does change the images in unexpected ways, I am proposing a "new" color system for personal computers.
The beauty of LAB is that colors are known and fixed inside a color space. Whether or not your device can reproduce that color is another issue. Mapping color gamuts is simpler, reproducing color is more accurate.
This benefits all users by making color reproduce more accurately.
LCD's render color differently than a picture tube, so it can take advantage of less gamma and render LAB well.
Especially those with color-savvy RIP's. It will improve your output rendering. You'll get used to color-correcting with LAB color pretty quickly. Most people object because they are so familiar with RGB or CMYK. If they started with LAB, they'd definetly complain about switching to RGB.