CMYK vs RGB RE: PDF query

[Davis, David]

Well Adobe's other software (Illustrator, InDesign, Photoshop) and even Microsoft's Office suite seems to find it a lot less "complex" than FrameMaker does....

A screen-shot in a technical manual does come from an RGB colour space. Likewise, a photograph taken with a digital camera is natively an RGB thing.  If they ever gets printed on paper on colour, then CMYK inks will be used to print it (there are no RGB inks!)
What's supposed to happen is that they can be included in your PDF output as RGB items, tagged with their respective colour profiles (sRGB for a screenshot, or something more fancy if the camera's manufacturer supplies their own profile), and the PDF is output-device-independent.
So if you view the PDF on screen, the OS and display driver take account of the monitor's declared output capabilities, and render the RGB items appropriately;
Conversely, if you're printing the PDF on paper, the OS and printer driver connive between themselves to choose appropriate CYMK values to render the RGB items on the page.
Trying to convert to CMYK up front in FrameMaker and thus pre-empt the printer's capabilities is a mug's game (and vice versa if you have natively CMYK or Pantone material in your PDF).


From: Craig Ede [mailto:craigede at hotmail.com]
Sent: 22 October 2014 15:35
To: Davis, David; framers
Subject: RE: CMYK vs RGB RE: PDF query



Yes, I think color conversions are that complex.
RGB was designed for monitors allowing a broad range of additive colors in the form of light (i.e. lit pixels).
CMYK was designed for subtractive printing to paper offering a restricted range of those colors; many of the RGB colors being "out of gamut" for CMYK, meaning there is no formula to convert them.
Nobody serious is printing high-quality hardcopy using R, G, and B inks. And I'm not sure why one would want to use CMYK to print to the screen.

Craig
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