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John Deubert’s AcrobatiX: A Color Management Primer

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Color management is a fact of life. Nearly all of the color we see on a computer display is adjusted one way or another before it reaches our eyeballs. Acrobat expert John Deubert looks at the basics of how this adjustment works.
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In the Beginning, there was Ink and color was Constant. Ink drawings on paper looked the same from one place to another, from one person to another, subject only to the current light source. A document could travel hundreds of miles and the color would remain constant, assuming it wasn’t rained on, spat upon, or subjected to some other trauma.

After ink came Pantone™, and color was Specified. You’d tell the press operator which particular Pantone ink you wanted for your artwork, and that was the color you’d get. It was still ink, you see, and so all was good.

Then came electronic documents, and color pretty much fell apart. Specifying color became separated from producing color, and we came face to face with an ugly fact: Our methods of specifying color were woefully ambiguous. A blue ox on one computer display (remember Paul Bunyan?) would look distinctly green on another and all bets were off when we printed it. We needed some way of translating colors from one device to another so they’d look reasonably the same.

This is the broad purpose of color management: translating color among devices so that they all look alike. This is a stunningly complex subject, and we’re not going to talk about it in depth here. However, because nearly everything we see on a computer screen is being color-managed, it’s good for us to know the basics of how it works, and that is what we’re addressing today.

Background: More About the Problem

It’s hard to think of any document-oriented application that doesn’t let you assign colors to text and graphic elements. Not only graphics and page layout software, such as Photoshop and Adobe Illustrator, but also spreadsheet, database, and simple word processing software let you assign colors to elements in your documents. Over the past decade, as cheap color inkjet printers brought color printing to nearly everyone’s desktop, the ability to colorize even the most mundane documents has become routine.

At this point, the design of application and system color pickers have stabilized; mostly they let you specify color in terms of RGB, CMYK, HSB, or other sets of numbers. (Although, my personal favorite color picker is the Macintosh Crayon Picker, Figure 1.) As you’ve certainly noticed, the colors you choose change their appearances on different devices. An RGB triplet will produce a different color on each display device to which it’s sent (Figure 2). Similarly for CMYK and other color values: a given set of CMYK values will look different—sometimes very different—from one printer to another.

Figure 1 The Crayon Picker is my favorite Mac color picker.

Figure 2 A given RGB or CMYK color spec will yield a different perceived color on different devices.

What this means is that you can spend hours and hours getting your design to look just right on your computer screen, but when you print it or send it to someone else to look at on their computer screen, you have no precise idea of what your document will look like.

Bummer.

The root of the problem is that red, green, blue, cyan, magenta, and yellow are not precisely defined. If you specify your color is made up of 30% red, 90% green, and 40% blue, you haven’t really said anything definite. Whose red, green, and blue are we talking about here? Whose phosphors, whose liquid crystals? And, of course, the same goes for CMYK: For what inks are your numbers intended?

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