Doug Kerr
Well-known member
From time to time, we see here discussion of a particular image in which the commenter mentions that a certain spot has a certain color, described in CMYK terms (and thus, perhaps, some different postprocessing would have been desirable).
This always seems to me to be inappropriate. For openers, our theory of color perception treats color as three-dimensional - three "coordinates" (under some color model) are needed to define any color - not four.
My understanding of the CMYK color description scheme (I hesitate to call it a coordinate system, since bona fide color coordinate systems have only three coordinates) can represent any specific color with an unlimited number of "quadruplets" (to use a mathematician's terms for suite of four numerical values). Said another way, a given color does not have a single CMYK description.
For example, any color within the gamut of a particular scheme can be represented with a CMYK quadruplet having a K (black) value of 0. Or with a CMYK quadruplet having various non-zero values of K - essentially arbitrarily.
The CMYK system is really intended to express a "recipe" for rendering a particular color following the principles of four color printing. There, conceptually, any color within the gamut can be produced by the appropriate densities of cyan, magenta, and yellow ink. But in reality, for one thing, true blacks are hard to actually achieve this way, and so for this reason, and others, black ink is used as well.
The appropriate black density to be used for rendering any given color (for example, a reflective color we can describe in three coordinates under the L*ab coordinate system) does not have a unique value. As I understand it, various algorithms are used in the printing process to determine this, based on balancing several criteria (and of course depending on the actual process to be used). (I think that even the relative costs of the different kinds of ink actually figures into it.)
Thus, while our image editing and manipulation software may take any pixel (perhaps represented in memory in RGB coordinates, or CMY coordinates) and report to us a CMYK "recipe", that is arbitrary.
Now, any defined three-primary "subtractive" color model (CMY) does have a unique "triplet" for any color.
But it seems that stating a color (not a recipe at the point where we are ready to lay down ink) in CMYK form is misleading.
So my thought is that, when the use of the "subtractive" type of color model is handsome because of the understanding it gives, we should describe colors of interest in terms of their C,M,Y coordinates, not their C, M,Y, and K values.
Of course, I don't really work with these concepts, so I may be barking up a wrong tree here. Perhaps real workers here in the realm of CMY and CMYK representations can let me know where I might have gone wrong.
Thanks for any help you can give.
This always seems to me to be inappropriate. For openers, our theory of color perception treats color as three-dimensional - three "coordinates" (under some color model) are needed to define any color - not four.
My understanding of the CMYK color description scheme (I hesitate to call it a coordinate system, since bona fide color coordinate systems have only three coordinates) can represent any specific color with an unlimited number of "quadruplets" (to use a mathematician's terms for suite of four numerical values). Said another way, a given color does not have a single CMYK description.
For example, any color within the gamut of a particular scheme can be represented with a CMYK quadruplet having a K (black) value of 0. Or with a CMYK quadruplet having various non-zero values of K - essentially arbitrarily.
The CMYK system is really intended to express a "recipe" for rendering a particular color following the principles of four color printing. There, conceptually, any color within the gamut can be produced by the appropriate densities of cyan, magenta, and yellow ink. But in reality, for one thing, true blacks are hard to actually achieve this way, and so for this reason, and others, black ink is used as well.
The appropriate black density to be used for rendering any given color (for example, a reflective color we can describe in three coordinates under the L*ab coordinate system) does not have a unique value. As I understand it, various algorithms are used in the printing process to determine this, based on balancing several criteria (and of course depending on the actual process to be used). (I think that even the relative costs of the different kinds of ink actually figures into it.)
Thus, while our image editing and manipulation software may take any pixel (perhaps represented in memory in RGB coordinates, or CMY coordinates) and report to us a CMYK "recipe", that is arbitrary.
Now, any defined three-primary "subtractive" color model (CMY) does have a unique "triplet" for any color.
But it seems that stating a color (not a recipe at the point where we are ready to lay down ink) in CMYK form is misleading.
So my thought is that, when the use of the "subtractive" type of color model is handsome because of the understanding it gives, we should describe colors of interest in terms of their C,M,Y coordinates, not their C, M,Y, and K values.
Of course, I don't really work with these concepts, so I may be barking up a wrong tree here. Perhaps real workers here in the realm of CMY and CMYK representations can let me know where I might have gone wrong.
Thanks for any help you can give.
