Each color space has a defined gamut – a range of possible colors. There is no single color space that can reproduce all the colors from the entire spectrum whether working in CMYK (Cyan, Magenta, Yellow and Black (which printers call “Key”) or RGB (Red, Green, Blue).
CMYK color spaces typically have color gamuts that are slightly smaller than RGB spaces. That means fewer colors, and usually less vivid colors. The benefit, however, is that a color space such as SWOP CMYK has a color gamut that is achievable by almost all CMYK printing devices. This is helpful in terms of color consistency if jobs are to be printed across different print devices. Keeping to a CMYK color space for line art or vector art can also improve the match from image color to spot color (such as PANTONE) and preserving or editing the black channel is also possible when the color space is CMYK.
RGB color spaces are generally larger than CMYK spaces and able to reproduce more colors that are brighter and saturated in color. RGB color spaces are the preferred color space when jobs are sent to the printer. Keeping files in RGB allows for greater variety of output options, such as web, press or digital print. RGB also means smaller file sizes, which can increase productivity. Most print devices use CMYK inks, however, so at some point the RGB elements will be converted to CMYK. The print shop can generally do the conversion at the RIP just prior to printing, which generally yields the most pleasing results.
Sometimes it’s possible to design artwork using CMYK colors to yield more precise matches and yet keep images in RGB spaces in order to retain more vivid color. RGB and CMYK elements can then be placed into page layout applications such as QuarkXPress or InDesign and then be output in such a way that none of the colors get converted until they should be, at the printer.
