Hey, what’s the difference between CMYK and RGB?



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As graphic designers we get asked ‘what’s the difference between CMYK and RGB? all the time…

Any coloured photograph, illustration or text is made up of either RGB and CMYK colour mode. RGB colour is used for digital communications on screens and CMYK is used for artwork for print.

RGB stands for the colours red, green, and blue. The RGB model is known as an additive model, where colours are added together to make up what we see on the screen. Basically, pixels on a television set or computer monitor create tiny pixels that, if viewed under a magnifying glass are made up of one of those three colours. Light is projected through them, blending the colours on the eye’s retina to create the desired colours.

CMYK stands for the colours cyan, magenta, yellow, and black. CMYK is a subtractive model. This gets a bit complicated, but the idea with subtractive models like CMYK is that colours from the spectrum are subtracted from natural white light into pigments or dyes. These pigments, then, are printed onto paper in tiny little cyan, magenta, yellow, and black dots. If you were to take a magnifying glass to a magazine cover, for example, you would see that the main image is really just a bunch of dots spread out, some closer than others, to appear like the colours we want.

Still with me? Let’s compare…

Instead of utilising ink to produce hues like CMYK colour mode doesn’t, the RGB profile partakes an additive process to produce colour by blending light. The presence of all RGB primaries at full intensity yields white, while the absence of colour produces black. When you turn a monitor or screen off, you see an absence of RGB colour, resulting in black. The colour displays on your screen result from the presence of those RGB base hues. Because RGB uses light it produces a larger array of colours; this colour profile features a larger gamut, or colour range, than CMYK. This is because all primaries mask to yield to a blackish hue. This process is similar to when you mixed paints and dyes to make that unsightly dark colour. As inks and dyes are layered upon each other, they subtract from the white of the paper.

Neither system of colour is perfect (neither can actually reproduce all the available colours in nature), but both are good enough to look very realistic to the human eye. You don’t really need to know all the technical stuff but you do need to know when to use RGB and when to use CMYK. If you create a brochure, for example, using RGB colour, when you send it to the printer (who uses large bins of ink that are made in cyan, magenta, yellow, and black), your colours won’t be quite right when printed. But don’t worry, this is our thing!

So to leave you with one final thought remember:

  • RGB for screen.
  • CMYK for print.