CMYK VS RGB



  • I'm having my flat colorist give me files in cmyk form, but then I notice CSP prompts me to convert it to rgb color data. (When opening a psd file)

    So does it matter anymore?



  • CSP doesn't have a CMYK color space. Having your flats done is CYMK is mostly useless since you'll be coloring in an RGB color space in CSP and then converting to a CMYK color profile when you export.



  • Thanks @garlam I guess that inks are so good these days that it doesn't make much of a difference these days ?



  • You need to know what CMYK color profile your printer is using. You need this profile to account for how the conversion handles ink saturation levels, dot gain, and so on. Set up your profiles in the Color Preview. With your CMYK color profile set up in the color profiles, you can periodically check the soft proof to see how the colors should look when printed on paper (or as close as an RGB monitor can get it).

    Unfortunately, with an RGB to CMYK color conversion, a little black ink will be added to the colors and that's not always so desirable. Some colors (burgundy for example) uses a little black but for the most part, K tones are not great. You can remove K tones before you export by going to the color preview and selecting the color curves. Select K and drag the right most point down. Dragging it down to 0 will remove all black from your colors, moving it half way will cut your black percentages by 50% and so on. What you could do is check your colors with the color picker while on the CMYK sliders to see how much black makes it into your colors. Under 15% won't show much but you wouldn't want that much in skin tones (it can make for a creepy green tone). When you soft proof with the black slider all the way down, your line art will look dull during the proofing but if you export your line art separately it can be printed in 100% black. Colors on screen will print darker anyway so you should be able to remove blacks altogether.



  • Thanks again @garlam - just to clarify - you recommend sliding the K level in addition to setting up the CMYK Profile?



  • You'll still need to set the correct color profile to suit the printer to account for things like proper ink densities, paper grades, and dot gain. Everything else is color corrections. If you print in North America, most likely you'll be using SWOP. If you print in Asia, it's usually Japan 2001. And in Europe it's mostly Agfa. You need to check with the printer to see what they use (you probably won't run into this but some printers have their own profiles which they will send to you). If you haven't shopped around for a printer yet then working in RGB is the way to go. You can color without having to worry about the CMYK profile and convert from RGB when you know what the CMYK profile is. But you'll probably need to do some color corrections before exporting.

    Reducing the K tone is part of the color corrections. Adding black to colors in ink doesn't make a darker color, it makes a different color (yellows become green, for example). CSP uses a fairly light Gray Component Replacement so it's not horrible but you need to check. Aside from the blacks, you may notice that a soft proof (preview mode) of your colors looks a little dull (I find Japan 2001 fairly dull in proof, for example) and you may want to make adjustments to brighten the colors a bit. Choose a light page, a dark page, and a normal (average) page and see if there's a correction you can do that would work globally to reduce blacks and brighten the colors to something you can live with that works on each kind of page.



  • @garlam super helpful - thanks! You rock!