Introduction
IntroductionColor match proofing is done by linking an ICC profile of the process to be simulated to an ICC profile of the process being used. It cannot be done with a single ICC profile of your printer.
This is very different from "pretty picture" color management. If your only need is to produce pretty pictures, you need only provide an ICC profile of your printer, allowing it to be used with a "generic typical" profile of a CMYK device, and a "generic typical" profile of an RGB monitor. This is a fine way to produce predictable pleasing results, but it can’t necessarily be expected to provide sufficient precision for color match proofing
Paper and InkMajor printer and paper manufacturers are known to change their paper coatings and ink formulations without notice. Small changes to paper coating or ink formulation will produce small changes in color response, invalidating any ICC profile that had been created previously.
The resulting failures can be insidious, in that these small changes leave a print that still looks “reasonable”, while it contains small color shifts that cause it to cease to be a match proof. This is probably the worst possible mode of failure in a contract-proofing application.
Since you can't count on the paper and ink manufacturers, you need to do your own quality assurance. Once you have produced and confirmed a good ICC device profile with a particular paper and ink, it is important to produce test prints and patterns and to keep them carefully labeled and filed.
Anytime you have reason for concern, reprint those tests with the same color configuration and carefully compare them to your filed copies. With some of the major printer and consumable manufacturers, you need to be concerned every time you open a new package of their product.
Don't trust the representations of paper and ink sellers when your critical contract-proofs are at stake. Software technology can't do this for you, it's up to you.
Pretty Pictures
The ICC profile that you specify for your printer is being linked with ICC "input" profiles that are hidden somewhere within the color management system. As long as those "hidden input profiles" are a match to the thing that you wish to proof, they'll get your job done. If they're not, you'll get "bad color."
Some inexpensive proofing solutions only offer this mode of operation, linking output device profiles to "hidden" input profiles. With Wasatch SoftRIP, you can set up your own defaults, or even more usefully, you can specify specific simulations as discussed below.
Match Proofs
If your input and output profiles are accurate at all three points, and if the color gamut of your printer is large enough, you can expect amazingly precise color simulations. Failure is almost invariably due to bad profiles. (See "Paper and Ink" above, for a discussion of how good profiles can become bad.)
A final and critical detail in the construction of color configurations for match proofing is the choice of "rendering intent." Wasatch SoftRIP provides full control, and you can read more about it under "ICC Rendering Intent", in the main manual for Wasatch SoftRIP.
Dots and Grainy
PrintsPrints with visible dots are always offensive due to their grainy appearance, but they have an even bigger problem in the color match proofing application. When the viewer can see the dots (in the form of "graininess"), the eye is not integrating the primary colors, and the perceived color shifts.
Grainy prints can result from a badly adjusted printer or a poor choice of dithering method. What is not commonly recognized is that they can also be caused by the color separation rules implemented by badly designed ICC color profiles.
The problem is very different in the large format and proofing worlds. In the large format world, prints are usually viewed from some distance, and dots are hidden for that reason. In proofing, prints are typically examined "in the hand", and the problem becomes much more significant. Color profiles that are suitable for one application may not be suitable for the other.
Random dot halftoning methods, such as Wasatch SoftRIP's "Digital Mezzotint", work by varying the distance between dots, rather than by varying the size of those dots. Such methods are necessary for proofing with color inkjets, but as dots become spaced further apart, they become easier to see.
An important way to avoid widely spaced dots is to confine the use of black ink to only the darkest shadows. This is critically important because black is such a strong colorant, and widely spaced black dots are so visible. When neutrals are printed with C, M, and Y instead of black, the dots of the weaker colorants are packed much more closely, and the overall quality and "smoothness" of the print increases substantially.
Most high-end color profiling software (software used for the making of ICC profiles) provides some control of the "GCR" or use of black ink. Careful attention to this issue is critical when making ICC color profiles for use in color match proofing, or for that matter in any application where the "smoothness" of the print is especially important.
A similar benefit is achieved by the use of light inks (particularly light cyan and magenta) in many of the current inkjet printers. The effect is simple - for any given density, light dots can be packed more tightly than dark dots. The light inks are used in highlights and generally wherever low color densities are required. Cyan and magenta are the strongest of the colored inks. The special visibility of these inks in the printing of flesh tones and yellows is the reason that one sees cyan and magenta chosen for the diluted inks in most of the six-ink printers. This is handled automatically by the halftoning algorithms in Wasatch SoftRIP.
Industry
Standards
Wastch SoftRIP works with ICC profiles from all ICC compliant color profiling software, whether Praxisoft, Monaco, Color Solutions, Agfa, Kodak, or others. These files, marked as ".icm" files in the above illustration, control color reproduction in Wasatch SoftRIP.
Wasatch SoftRIP also provides a choice of "CMM" (Color Management Module), from the following manufacturers.
This is the software component that reads and applies the data contained within your ICC profiles. The Microsoft (Linotype) module is included free of charge in Windows 98 and Windows 2000. The others are available as optional "plug in" modules from Wasatch, at a small extra cost.
The choice of CMM actually makes less difference than one might imagine. We've conducted extensive tests with the above three, and it hardly matters.
ICC based color match proofing really does work, producing prints that are identical to within remarkably small Delta E. The magic, the thing that controls your color, is the data contained within your ICC profiles. The effort that you put into the creation and management of those profiles is what will make or break your success with inkjet color proofing.