On Tue, 24 Jun 2008, Martin Tlustos wrote: > I followed the thread about the real black in cmyk. Am I right in the > conclusion that as far as possible it would be better not to mix rgb and cmyk > in a publication, or does that depend on whether you mix images and graphics? > Thanks for the explanation!
If it is at all possible, DO NOT MIX RGB AND CMYK. It's not just white point. There are a lot of issues that can come up with using the RGB color space for print media. Some sRGB colors ar out of CMYK's gamut, and some of CMYK's colors are out of RGB's gamut. Pure RGB black, as you can see, is not actually converted to 100% K, but 87/79/64/93 (which GIMP describes as having a hue of 219) and looks blue at higher values. If you intend to print something out, always use CMYK. Whatever software you are using will have to convert to CMYK anyways, because that is what the separations will have to be, and those are the colors of the inks that the printer/press will use, so starting CMYK can only help. The advice for work that is displayed on a computer screen is to stick to RGB, since that is what screens use, but there are benefits to having that be CMYK, as well (for me, the addition of the K channel sort of acts as a separate value channel, which can be useful for brightening an image without introducing color shifts--I would love to see RGBW as a proposed standard). There's also the possibility that it will mask some errors that won't be visible until press time. For example, I went into GIMP and created a red image (255R/0G/0B), imported it into Scribus and created a red box. Both are similar colors, and you might not notice any discrepancy until you get the plates back from the printer and for some reason, you've got both colors scaled back to a 90% linescreen, causing that nice, clean edge on the font to become ragged. So CMYK for print work. RGB for screen work. But above all else, if ot's possible, do not mix. -- | Andrew A. Gill To ensure continued quality of service, | | this e-mail is being monitored by the NSA | | <superluser at frontiernet.net> <http://www.needsfoodbadly.com> | -- Never mix, never worry.
