Understanding Color Models - 2 CMYK
In tutorial we looked at the RGB model and we saw that one great advantage of this was that by digitizing the inputs you can create an immense array of color variation
The opposite model of RGB is CMY. This is back to our childhood paint mixing method. Printing inks are based on this CMY model. With this method when you add the three primary colors together, in theory you get black. Not white, but black!
Why is this?
The reason is because the pigments in the inks are absorbing all colors except their named color. So magenta absorbs all colors except magenta (reddish). So it absorbs cyan (light blue) and yellow and just reflects back magenta to our eyes.
Therefore when you add cyan to magenta, you actually reduce the amount of color variation being reflected back. This is why adding pigments is called subtractive method.
Adding cyan to magenta will cause all of the yellow range to be absorbed and also half of the magenta rand and half of the cyan range. When you add the yellow pigment, there is no yellow light to be reflected because the other two colors already have absorbed it all. Furthermore the yellow ink absorbs the remaining half of magenta and of cyan leaving no color to be reflect back at all - so you get black.
Of course that would be the case if you could get perfect magenta, cyan and yellow. These colors do not perfectly occur natuarraly so due to the imperfections in the colors we get a dark muddy brown rather than black.
You can see the theory of it in the diagram.
In fact the same effect with projected light would be acheived if you took those colored glass filters that we mentioned in the first tutorial and instead of using three flashlights, you just uesed one.
With the first filter, the red, on the flashlight you are filtering out all color except red. Add the blue filter on top and it gets darker, with these two filters in place yellow as been completely filtered out so when you add the yellow filter there is no yellow light to get through, furthermore, the yellow filter blocks out the remaining parts of reds and blues so no light gets through, darkness... black.
As we said earlier, colors are not perfect, we can not get perfect cyan, magenta and yellow CMY: so black can not be achieved perfectly from mixing pigments. Therefore black ink is added to get solid black.
The outcome of this process is the CMYK model and k stands for black color, which is also recognized as 'key' color. Hence the model is called subtractive model. Print production is based on this CMYK model.
It is useful to have proper understanding of the color models. The monitors as well as scanner works on RGB principle. While scanning we can adjust the software to produce desired result. CMYK is for print industry. It cannot produce the color range of RGB hence after finishing the work on computer in RGB mode when you convert it into CMYK for printing some tonal changes can occur. In spite of its limitation CMYK model is considered as the best model available for printing because it can produce high quality finished output.
Personally I found that understanding how colors works together in the two models helped me with graphics and graphic design.
I hope that you have also benefited from these two tutorials.
All the best.
Liz Green.
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