Converting RGB to CMYK
April 10, 2008 5:00 AM   Subscribe

I am designing a card in photoshop, starting out in RGB then converting it to CMYK for print. The RGB looks vibrant and beautiful but the CMYK conversion is lacking contrast and the colors are washed out. Anyone have any ideas on how to maintain the beauty of the RGB image in CMYK?
posted by aisleofview to Media & Arts (17 answers total) 5 users marked this as a favorite
My first reaction is: Don't design print in RGB. My second is: you will never, ever, get the same palette from both color spaces. Take a look at the wikipedia entry for Color Spaces if you don't get this.

With that said, the only real way to get the colors to do what you want is to work very, very hard at color matching your screen to your output device. You don't say if this is a professional press, or just a home printer...big difference in how you'd do one over the other.

Notice that I didn't say matching your output device to your screen. You need the display to give you the closest look to your output you can.

If this isn't a professional job, and you don't want to both with expensive color matching stuff...convert to CMYK, and then play with curves to set the black point of your design slightly lower, then play with contrast. But you'll never match them, not truly.
posted by griffey at 5:25 AM on April 10, 2008 [2 favorites]

I hate to say it, but you should probably have started in CMYK if you're working for print. Some RGB colors just don't reproduce faithfully in CMYK because they're two difference colorspaces. You may also want to bear in mind that the brightness of an image shown on a backlit monitor simply doesn't exist in a printed piece, and that the colors of your card shown on your monitor may well be just fine when the ink hits the paper.

Have you tried running an inkjet proof?
posted by MegoSteve at 5:29 AM on April 10, 2008

thirding don't work in rgb. either convert now and adjust contrast to match as closely as possible or rebuild the file.
posted by patricking at 5:32 AM on April 10, 2008

4thing don't work in RGB, if it's destined for print. It's just easier to stick with the final output gamut instead of being disappointed by the conversion.
posted by Brandon Blatcher at 5:35 AM on April 10, 2008

When designing for CMYK output, you really have to start with CMYK.
posted by Fuzzy Skinner at 5:35 AM on April 10, 2008

Back when I worked in print I had some good luck exporting the RGB piece to a CYMK PDF via postscript printer. I would have inserted that as an image, so I don't know how it'll look as a standalone document to print. But it's worth a shot.
posted by Mayor Curley at 5:40 AM on April 10, 2008

Similarly, do not take a CMYK image and put it into RGB, you'll be shocked at how washed out it looks. Some things just have weird colorspaces, like designing images being displayed on an NTSC TV (it's hideous).

To understand the colorspace problem, let me suggest a highly inaccurate metaphor that will nevertheless illustrate the situation. Imagine RGB as a simple cube, with red, green, and blue as the axis. Next, imagine a different shape, (sort of) a tesseract thing, wherein the black (K) is not perfectly black hole black, but like ... a good charcoal. Both shapes are about the same "size."

Now rotate it at some angle and try to put it inside of the RGB cube. The RGB cube has some corners that the CMYK shape cannot reach. Similarly, the CMYK has a few bits poking out that the RGB cube does not serve. I'm sure of the former, mostly sure of the latter. You simply cannot get some of the pure resonance of RGB out of CMYK.
posted by adipocere at 7:11 AM on April 10, 2008 [1 favorite]

Thanks all...some effects in photoshop will not work in CMYK so I decided to design in RGB. Alas I am going back to the piece and remaking in CMYK. Another lesson learned
posted by aisleofview at 7:28 AM on April 10, 2008

Starting in CMYK won't help you. The colors still won't be as vivid. You'll just be more used to them since you started the whole process in CMYK. I say just convert it; why throw out all the work you've already done?
posted by zsazsa at 8:04 AM on April 10, 2008 [1 favorite]

zsazsa makes a pretty good point, actually. You may be able to tweak the RGB version to compensate for the CMYK output. But, rather than compare one to the other, ask yourself if the resulting CMYK output looks fine to someone viewing it who is not comparing it to your RGB file.
posted by Fuzzy Skinner at 8:20 AM on April 10, 2008 [1 favorite]

Sorry you have discovered a sad truth about print output. (My partner *hates* doing print design / layout for this very reason).

Thirding zsazsa, once you are in CMYK, try increasing the saturation and adjusting levels.

Make sure you get a reasonably accurate proof on similar paper to your final output -- I've found that a Kinkos color print on glossy paper is reasonably close to the results I get from my print house (and much cheaper than a calibrated proof from them.)

Finally, I'll second Fuzzy and recommend you try to forget how nice the RGB version looked on your screen.
posted by omnidrew at 8:31 AM on April 10, 2008 [1 favorite]

Btw, see if you can find a colour profile for your printer and paper. That might help somewhat.
posted by Magnakai at 9:33 AM on April 10, 2008

For print, I work with RGB images using the CMYK preview (command-y), and I'll bump the saturation before making final seps if the colors are looking washed out, even if that means it looks almost neon in RGB.
posted by Dean King at 9:45 AM on April 10, 2008 [1 favorite]

Welcome to the wonderful world of RGB-to-CMYK conversion, known to a lot of us as a customer screaming "It looked great on the screen and horrible in print!"

There's no easy way to do it. As you mentioned, many Photoshop effects are simply not available when working in CMYK. If you are using adjustment layers, things can get REALLY screwed. One thing that does help me sometimes is that I will keep the live PSD in RGB format. When I need to convert to CMYK, I first save a copy, and then convert the copy to CMYK. When it asks if I want to merge the layers, I click "yes." This way you still have a live original and a CMYK version that's about as true to the original as you can hope to settle for. (Remember - settle for.) Also, once you have a final CMYK image, try this - pull up Levels, choose the black channel in the Levels dialog, and bump the left slider to 15. See if you like the way it comes out. It doesn't always help, but it has helped a lot of my images by pulling in a little more black in the darker areas, giving some more contrast. Of course, I work mostly on newsprint, with horrendous dot gain, so this is a definite case of YMMV.
posted by azpenguin at 12:01 PM on April 10, 2008 [1 favorite]

Troubleshooting section

Your output device will make a big difference here. If the piece is going to be output on a laser printer then there's a chance that designing in RGB will be fine and might actually give you better results. Many laser printers and other print-on-demand devices use extra inks (CMYK plus, for example, Light C, Light M, and Light K) that will translate the RBG colorspace semi-accurately. Some desktop laser printers take the fact that non-designers commonly do layout and design in RGB and are built to accommodate this. (This is not a dig at you by any means, please don't take it as such.)

However, if you're designing for press you're most likely stuck with CMYK, though some RIP systems do accept LAB images which, theoretically at least, produce a more vibrant color on-press.

You say that the CMYK conversion is lacking contrast and the colors are washed out, but do you mean on-screen or on your hard proof? If you mean that it's not satisfying you on-screen, is your monitor calibrated? Even a quick-and-dirty calibration can make a huge difference in how you work and how the files turn out. I can't speak for Windows systems, but Apple computers have a calibration feature built into the Displays system preference. If your hard proof isn't making you happy, what is your proofing method? Is the proof from your service provider, or are you printing it out off a desktop printer? A lot of questions, but this is basic troubleshooting here in the prepress department.

Advice section

As to how to avoid bad conversions, commonly super-saturated areas of color don't convert well, especially when created in Photoshop. Reds, greens and blues will either end up muddy or really weirdly over-saturated and flat. This pic from the Wikipedia article that griffey linked to shows that the red, blue and green extremes fall outside of the printable spectrum.

If you design with the idea that your colors will be muted, you can turn this to an advantage rather than a detriment. Realize that you will never get that SCREAMING RED!!one! that you're looking for. Similarly, especially when using Photoshop, you'll have a hard time getting a rich black without using so much ink that you end up turning the paper to mud. But that still leaves you with an entire spectrum of lavenders, indigoes, forest greens, dusty roses, and all manner of other colors to work with.
posted by lekvar at 12:59 PM on April 10, 2008

Damn, all that blathering on and I failed to mention the two easiest means of determining whether your color will print well.

1) When you're in the color picker, a yellow yield sign with an exclamation point will pop up when the color you've selected is out of gamut for printing. If you click the yield sign Photoshop will select the closest color that will print.

2) Your Info palette should be bisected down the middle. The left half will show you your current color values in whichever colorspace you're using. The right half will show, or can be configured to show, the current CMYK values. If the current value is our of gamut, exclamation points will show up next to the CMYK values.
posted by lekvar at 1:09 PM on April 10, 2008 [1 favorite]

There's a lot of great advice and input here. I'll add another penny or two:

Be sure you are talking about the difference between RGB and CMYK, and not just "looks great on my (backlit, vibrant) screen, and looks crappy on (dull, reflection-lit, ink-soaking) printed paper. There are so many variables in printing that it's impossible at times to take them all into consideration without trial and error. I'm working on a project for a big national meeting. The logo and design uses the most difficult color of all to color-match: brown. I have to print some things on a Xerox DocuColor Copier, on various kinds of paper. Other things will be plotted on an HP 800 wide format plotter. Some of the plotting will be on paper, and some will be on cloth banner material. And all these things have to match as closely as possible. So, my on-screen image for printing to the Xerox on 65# card stock will look entirely different than the image I am printing on cloth on the HP plotter. This is why good color management (which my office does not have) is so important.

Don't be afraid to experiment. Good luck.
posted by Fuzzy Skinner at 3:22 PM on April 10, 2008

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