What is CMYK in Printing?
The CMYK acronym stands for Cyan, Magenta, Yellow, and Key: those are the colours used in the printing process. A printing press uses dots of ink to make up the image from these four colours.
‘Key’ actually means black. It’s called Key because it’s the main colour used to determine the image outcome. Black ink provides depth and shading, whereas the other colours create different colours on the spectrum depending on how they are mixed. For example, cyan and yellow create a green when one is overlaid on the other.
What Does ‘Key’ Mean in CMYK?
There’s some argument regarding the origin of ‘Key’ to mean black. Some people say it’s because representing black with ‘B’ could confuse it with ‘blue’, but this is unlikely. It may be because the black plate is the ‘key’ plate on a printing press that aligns the other three colours to it (so the layers match up perfectly for the final image). This means any colour plate, in theory, could be the ‘K’ in this process, if black were not being used.
A further argument suggests that ‘key refers to the very old presses way back in 1843 that used screw keys to determine the amount of ink required to achieve the desired end result.
CMYK printing is the standard in the industry. The reason printing uses CMYK comes down to an explanation of the colors themselves. CMY will cover most lighter color ranges quite easily, compared to using RGB. However, CMY by itself can’t create very deep dark colors like “true black,” so black (designated “K” for “key color”) is added. This gives CMY a much wider range of colors compared to just RGB.
The use of CMYK (cyan, magenta, yellow, and black) for printing has become kind of a trope for printers. But the reason why printing uses CMYK isn’t that well known, even to many graphic designers.
On the surface, it doesn’t seem to make sense. You might even have learned in elementary school that the primary colors — red, green, and blue (RGB) — are the primary colors, from which all the other colors come. After all, monitors, projectors, and television sets use red, green, and blue (RGB) to create all the other colors. Mixing some of these colors produces the secondary colors — cyan, magenta, and yellow. Mixing them all produces white.
Primary colours however, are arbitrary. There are several competing color models, and the theory behind color is quite complicated. However, partly for historical reasons, and mostly because most electronic screens are dark, we use RGB color models for most light producing imaging devices such as monitors and projectors. Combining red, green and blue light produces lighter colors, offering a good contrast to dark screens.
What does RGB mean ?
RGB means Red Green Blue, ie the primary colours in additive color synthesis.
A RGB file consists in composite layers of Red, Gree and Blue, each being coded on 256 levels from 0 to 255. For example, black corresponds to the levels R=0, G=0, B=0, and white corresponds to the levels R=255, G=255, B=255. The RGV system is used by the screens, the scanners and the digital cameras.
What is the difference between RGB and CMYK?
Both RGB and CMYK are modes for mixing color in graphic design. As a quick reference, the RGB colour mode is best for digital work, while CMYK is used for print products.