CMYK vs. RGB

[saria]

Quick question for everyone: If I'm designing maps in Gimp - with the end goal to sell as PDF's, but I also want to make them available for print on demand - should I be base painting in CMYK with Gimp? Or should I just do it RGB and then convert to CMYK?

Also - Does anyone here use Gimp who might be able to tell me what they draw/paint in and what the right option is? I'm still learning all the ins and outs here Thanks!

[Azélor]

Don't convert it from one format to the other because it will look awful. Pick one and stick with it.

[xpian]

RGB is a broader color gamut, meaning that it can represent more total color. However, the fullness of that color can only be truly experienced on a monitor or projector of some sort.

CMYK is a slightly narrower color gamut which ironically takes slightly more data to encode. The colors in CMYK will never be quite as rich and luminous as in RGB, but there's a reason for that. CMYK is all about printing. The RGB file you create on your computer will always be converted (usually by the printer itself) to CMYK as it's being printed out. Always. You may not be aware that it's happening, but it is.

That technical detail out of the way, the main question for you is one of workflow. If you want to work in a calibrated state where what you see on your monitor is as close as possible to the finished, printed color, then you might choose to work in the CMYK color space. Some graphic designers do this. If the whole point of the graphic is to be printed, then there's no point in enjoying the pretty, extra rich color you get from RGB.

However...many of us, whether we're professional illustrators or graphic designers, work in RGB because it's simpler and perhaps a little more standard. We create graphics that we want to look good on the web, and on tablets and phones. We understand that our beautiful files are going to look slightly duller when they're printed--that's just what happens when you print things out. We trust that the automatic gamut-conversion software contained in printers and printer drivers is very, very good these days, and doesn't need much babysitting to achieve good results.

I'd say, stay with RGB unless you have a very good reason to go CMYK, and don't bother trying to convert files from one color space to another unless you're specifically asked to do so by a printing professional or graphic designer who really knows what they're doing.

[arsheesh]

Xpian's already given a great explanation here. But to your other question, I'm primarily a GIMP user at this point (though I dabble in other programs) and I always work in RGB and then if needed convert to CMYK. In fact, I may be wrong about this, but I think that unlike Photoshop CS, this is the only color space you can currently work in in GIMP (converting to CMYK in GIMP requires a special filter and this is not a non-destructive process).

One thing you should know up front is that the current stable version of GIMP (2.8 something or other) only has limited tablet support. We are told this is an issue that will be rectified in the 2.10 release, but there's no telling when that will be (though they just released an experimental 2.9 version, so I'm hopeful it's not too far off). So if it is painting that you are interested it may be best to look at other options. One really nice free option worth checking out is Krita a robust paint program with a powerful brush engine.

Cheers,
-Arsheesh

[saria]

This has been great information - thank you to everyone who responded! Really appreciate it. I think that means I'll be doing it in RGB and dealing with the rest later.

It also brings up more questions, but I'll work those out as I go along!

[johnvanvliet]

for moving between color formats i normally use Nip2 -- a gui front end to the vips image library
http://www.vips.ecs.soton.ac.uk/index.php?title=VIPS
this also now supports imagemagick built in using the magickwand API ( i use a custom built Q16 and Q32 bit imagemagick )

or

i use Gmic
http://gmic.sourceforge.net/

gmic RGB_Image.png -rgb2cmyk -o CMYK_image.raw

outputs a 32 bit 4 band RAW image

or use "-o CMYK_image.tiff" for a 32 bit 4 band tiff image
or use "-o CMYK_image.tiff,uchar " for a 8 bit 4 band tiff image
or use "-o CMYK_image.png" for a 8 bit 4 band png image