Color Spaces - CMYK
As I mentioned in the blog last week, I am taking a little holiday break from writing the street photography blog. The small lessons in Color Theory are continuing. Color theory is a fairly complex subject. My brother in Texas helped me puzzle out the difference between color and saturation. My son from NYC is helping me work through issues on color spaces. It is tremendously fun to have family collaboration.
Color Spaces
The three color spaces that will be considered here are CMYK, RGB and HSV (B). Understanding color spaces helps make it clear how light mixes to get different colors.
CMYK
The CMYK model is used for pages and printers. The acronym CMYK stands for Cyan, Magenta, Yellow and Key. In traditional printing, the Key plate holds the details of the print. In CMYK this is usually done with black ink, hence the word Key actually refers to Black. Black is the “key”, i.e., the main color that determines the outcome of an image printed in the CMYK model. The other three colors mixed together produce new colors. Black creates the shades and depth of the image.
In CMYK printing, tiny dots of color are printed in a pattern small enough that the human eye perceives it to be a solid color. A process called half toning is used by a printer to blend colors or create shades and tints. Printing different colored dots in close proximity appears as a completely different color depending on the light filtering properties of the color. The spacing and size of the dots can create more or less saturated color. For example, dots of magenta spaced farther apart produce what the human eye sees as pink. A dark magenta shade can be produced by mixing Magenta dots and Black dots.
CMYK uses the subtractive method of mixing light to create color. Pages do not emit light. They only reflect light. Adding ink in the form of very small dots subtracts light reflected from the white page. Magenta ink subtracts out the green light that strikes the page. Cyan ink subtracts out the red light. Yellow ink subtracts out the blue light. For example, if we want to create red in the CMYK model we mix Magenta (red and blue) and Yellow. Adding the Yellow to Magenta subtracts out the blue, leaving only the red light to reflect off of the page. Adding Cyan to Magenta leaves only blue light to reflect off of the page because Cyan subtracts out red and Magenta subtracts out green.
As a theoretical issue, if you mix Magenta, Cyan and Yellow, you have no red, blue or green light being reflected and the mix looks black. However, in printing it is not possible to get a pure black by mixing the colors, so black ink is used. Aside from producing a better black, it requires less ink than if a color mix was used to produce black. Also, black is used for text and you can get more precise lines with black ink than you can with a mix of colored inks.
I hope you have a safe and fun New Year’s Eve celebration. I wish you health, happiness and good shooting in 2022.