Colorful Confusion in Graphic Arts
With few exceptions, your assets should not be in CMYK—even for print
I've worked with and taught graphic designers, illustrators, and photographers for decades. For almost all of this time, I've had to combat archaic habits and workflows and persistent myths about how color actually works. I've written long articles about this that are usually rather science-y. As evidence in favor of modern workflows, I use the books I’ve built and successfully sent to press. But here, I want to be more conversational and relatively brief.
The Myth: For print, a desired color must be represented by CMYK percentages
Many would say that 70C 30M 100Y 15K represents a specific green. But they’d also point out that you'll get a different green everywhere it's printed. For example, if I print it on my office's laser printer and at a commercial printshop, they won't match.
How can that be a specific color, then? Sounds like a case of cognitive dissonance to me. Also, when speaking to folks who perpetuate this myth, it's like we've passed the gates into Danté's hell:
Abandon hope all ye who enter here
One hears a lot of negativity disguised as cynicism:
"It will never look as good as it does on screen"
"You'll never match that color in print"
"Of course it looks different on your laser printer than it does on press—or anywhere else"
So depressing. Yes, all that would be true were it not for tech we've had for decades.
The CMYK values for that green (70C 30M 100Y 15K) aren't any more precise than the phrase "the color of Buffalo grass." We want a specific color appearance. The only numbers that truly describe a color that humans see are Lab values. The Lab color space (range of color) was made to reflect what the human eye can usually see. To explain it would require another essay, a chapter in one of my books, or other resources. Most of us feel more comfortable with the relatively intuitive RGB and CMYK, so I’ll stick to those. But here’s the rub:
RGB & CMYK color numbers don't mean much unless we associate them with a specific output device.
That’s because many factors affect how the color will actually look: The color and absorbency of the paper used, the brand of inks, how many inks, or, if viewed on a screen, its brightness (and just what kind of stuff is glowing in it), the amount and color of ambient light, and more.
In the bad old days, I worked in a print shop of sorts. On one device, we'd print an extensive color chart each morning. If a client needed us to match their corporate color, we'd find it on the chart and use the numbers used to achieve it. Luckily, there's a better way now: Software "looks up" the numbers that a device needs to achieve a given color.
Profiles: Giving Meaning to the Numbers
These days, we can still print color charts. Actually, the manufacturers do this so we don’t need to. These charts are scanned by cool devices that reads each color chip. Software associates each visual color with the numbers used to make it and generates a data file called a profile for that device.
Actually, this is done for each paper used by a printer. For my Epson SureColor P800, there are profiles for "Ultra Premium Presentation Paper Matte," "Ultra Premium Photo Paper Luster," and others with equally verbose and pretentious names.
So we at least stand a chance of getting the same color on each of those papers. Since other manufacturers do this as well, I can match colors with various printers, papers, and inks.
You can also make a profile for a display by dangling a similar device in front of it while software presents dozens of colors to the device. So many numbers! Luckily, computers handle numbers well. Software like Adobe Photoshop can use the profiles for your display and your printer/paper combo and show you an approximation of the final output (soft-proofing, it’s called). Turns out you can match on-screen what you'll see in print.
To summarize: Profiling a device is measuring its color capabilities and limits (its gamut or color space). The profile allows us to supply that device with the numbers it needs to produce the colors we want. We can use a manufacturer’s profiles or generate custom ones with help from others.
Calibration: Hacking the Hardware
Calibration. You've heard that word before, haven't you? Many conflate it with profiling as in, "do you calibrate your monitors?" or other personal questions. Calibration is adjusting a device, physically altering it, often to match a standard color space. We often use the same color-measuring hardware and software to first calibrate then profile a display so we know how far off its abilities are from the color space we sought.
You've heard of some of these standard color spaces, too, I'll wager: sRGB, AdobeRGB, DCI P3. Each of those is described by a profile. If you have a fancy display that produces color in a way that matches DCI P3, you know it matches every other P3-standardized display.
Commercial presses have standards, too, though "calibrating" presses is tough work. Gray-balancing and other elaborate adjustments are made to help them conform to standards with catchy names like Coated FOGRA39 or Coated GRACoL 2006.
In Our Software
If our hardware can be wrangled into these standards, you can imagine how much easier it is to tell a piece of software to conform to standards as well: We simply choose a preset.
Since I create RGB images in Photoshop and [mostly] RGB graphics in Illustrator, the presets I fuss over are for RGB color spaces and their profiles. The specific setting depends on the project:
sRGB is best for projects destined for both print and screen media (eBooks or websites).
AdobeRGB is made specifically for high-end printing and is thus well suited for it.
P3 color spaces are terrific for images destined for cinema or other displays that can show rich color. Images and graphics for mobile apps, perhaps.
When I choose to print, software like Photohop interacts with my printer's software, with one converting from a standard like AdobeRGB's color numbers to the numbers needed by the printer to produce the same colors. I often pull my images and graphics into InDesign which harmoniously houses RGB, CMYK, and other assets at the same time. I can say similar things about Affinity Publisher, and other software, too. I treat my software like another RGB device in the chain.
When I create a PDF that is sent to a commercial press, my images' RGB color numbers are changed into the CMYK numbers that a particular press needs to match my images' colors. I build entire books this way. Yeah, sometimes the press can't match the original, but often it can, and it's always as close as the physics allows.
Back to the original myth....
Do you need to use CMYK? Rarely.
When? Only when the the ink values matter more than the visual color. Example: one- or two-ink builds for small type (including black-only) and some few graphics. That’s about it. All else is in RGB.
I hope this little essay helps dispel the myth, and gives a glimmer of hope, though there’s so much more to learn about color management. It can get a bit steep at times if you want to go deep. If you do, keep in mind these basics to keep you oriented.