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Posted: Sun Jan 25, 2009 5:26 pm
by mikemeister_admin
Quote: "Use Curvemeister's wgCMYK curves on this image, setting GCR to light, and see how CMYK gives you individual control over each color. Add more K to the mix, and see how you can control the shadows."
What does GCR stand for? How does it work? What is K? How do I add it?
Bit confused.
Thomas
PS I think medium GCR works best on this picture but now idea why? DS
Posted: Sun Jan 25, 2009 5:51 pm
by Gary
Thomas I'm going to stick my nose in here. I think GCR probably stands for Green, Cyan and red, K is black. Could be wrong.
Gary
Posted: Sun Jan 25, 2009 5:55 pm
by Gary
Looking at it again I think I am wrong.
Gary
Posted: Sun Jan 25, 2009 6:34 pm
by Gary
Thomas I am sorry for the dumb reply above, GCR stands for Gray Component Removal, I found it at the bottom of the wgCMYK curves and it is found in the help files.
Gary
Posted: Sun Jan 25, 2009 6:40 pm
by ggroess
Indeed you are (Sorry)
GCR stands for Gray Component Replacement. (Professional Photoshop 5th edition)
It is the base amount of black ink hitting the page in a press printed image.
To get your mind around CMYK you have to remember that the CMY are color complements to RGB; exact opposites....K is the Black ink...K is one of the stronger tools we have in color correction it is extremely useful as we will see in the coming weeks. K give the image POP and fullness.
In press printing there are limits to the amount of ink you can put to a piece of paper under a given process. Let's say for discussion the limit is 120 to create an image you not only use CYM inks at various levels you also need to add black...the total of the inks cannot exceed 120 so you might have 20C 50Y 40M this leaves you with being able to add 10K to the mix to darken the shadows and make the overall colors richer.
You could add 3 to each color above to get the same 120 but the shadows would look flat and gray.
GCR gives you control over the amount of K adjustment you are applying to the image.
Greg
Posted: Sun Jan 25, 2009 7:17 pm
by mikemeister_admin
If I read you correct, if I want to increase K I should add GCR?
Or should I adjust the black curve or both? Sorry for still being bit confused. Maybe on a higher level.
Thomas
PS Greg. Thanks for a good try. DS
Posted: Sun Jan 25, 2009 8:52 pm
by ggroess
Kind of....
Changing the GCR changes the "saturation" of the K channel. In effect it adds more black to the black....but you have to remember it is a ink value. How heavy the black ink is allowed to be used in the image.
Lighter values require you to add CMY to the image to get to the same response.
Greg