CMYK is not an ideal working mode. I’m just going to take the chance to put my foot in my mouth and say NEVER work in CMYK.
Gripes:
CMYK works with four colour channels instead of RGB’s three. When you have many layers: Photoshop needs to process an extra layer for every effect applied. Working in CMYK might be the fastest way to convert 4GB of ram into 3GB of RAM, 3GHz into 2.4GHz and sanity into insanity.
When to use CMYK:
DON’T. I’ve only worked with one person who mastered the CMYK process. He owned his own plotter (most people call it a large format printer), specialized monitor and studio outfitted with SoLux lighting.
If you must to go down the CMYK road…. please note that it only makes sense as a final step — right before you print. Don’t seek out CMYK —- CMYK will find you.
-dv
Resources:
Printer test page (JPG & TIFF): http://books.outbackphoto.com/DOP2010_03/printer_tests/
The frugal student’s 1 inch plotter images (combined make 42” @ 300dpi)— http://voshart.imgur.com/1_plotter_tests
