process & workflow: Implementing Color Management in a Wide-Format PSP

If you're thinking about implementing color management in your wide-/grand-format print shop, the first question you might want to ask is: Just what exactly is color management?

In answering what color management is, it might be helpful to start by answering what it is not. Color management is not color matching. It's not color manipulating. Color management is not printing a bunch of swatches and matching one of those swatches to the color you hope to print.

Color management isn't any of those things because in actuality color management isn't color management at all. It's numbers management. That's because once color goes into a computer, it ceases to be color and becomes numbers; numbers that relate to how a color is going to be reproduced in a particular color space. What color management does is account for all the number transitions from color space to color space in a digital color workflow.

What's a Color Space?

A color space is a group of colors and some means to define them.

Color spaces are important because every device that reproduces color is going to have some colors it can reproduce, and some it can't. These colors are going to vary based on any number of factors, such as, for instance, type of media and amount of ink.

The colors a device can reproduce are known as its gamut. Once you have colors in a gamut, you need some way to define them. If you define them as red, green, and blue values, you've got an RGB color space. If you define them as cyan, magenta, yellow, and black values, you've got a CMYK color space. And the values, in digital imaging, are represented as numbers. That is, after all, what "digital" means. Further, RGB and CMYK are the spaces we wind up using in this industry not out of choice, but out of necessity. Necessity because RGB and CMYK are the colorants our devices use to reproduce color. If you're going to attempt to manage color, you have to have a way to quantify how every device in your workflow reproduces color with its colorants in every situation in which you use it.

Next, there are two distinct definitions of color spaces you need to consider in implementing color management.

There are standardized "working color spaces" in both RGB and CMYK. They represent approximations of how various devices might reproduce colors, but they're not representative of any particular device. In addition, there are "device profiles" which can be RGB or CMYK depending on the device in question, that are unique to the situation and the device with which they were created. These are your specific device profiles—monitors and printers, for instance—in your workflow.

Both standardized working color spaces and device profiles are defined to all your applications that are "color aware" (that can use color management) as ICC profiles.

What's an ICC Profile?

An ICC profile is a computer file that tells color management engines how to render color into a particular color space.

Every device in your shop produces color from some set of primary colors, in some particular way. Each particular way is going to vary depending on certain factors, and each particular way is going to be different. Since each way is different, somehow or another each way for each device needs to be calibrated for each of its color reproducing conditions—such as media, ink resolution and density for your printers, and such as gamma, white point and luminance for your monitors—and then characterized (profiled.)

What all this boils down to is that while your shop and all the color reproducing devices and situations in it are unique, the rest of the world is not your shop. So your job, and the job of color management, is to get the colors of the rest of the world into the color spaces of your shop with its color information uncorrupted and hopefully undiminished. This is accomplished by moving files from however they came to you from the outside world into first your standardized working color spaces, and then into your unique device color spaces (ICC profiles.) It's how and when you make these color space moves, and how good your device profiles are, that will determine how well you do the job.