Why RGB isn’t CMYK

26/01/2008

Color properties can be confusing, especially since many designers use the computer to design for print. Unfortunately, the color associated with computers – RGB – is not the color that is associated with print – CMYK. Here are a few tips to help you remember the difference between the two color systems:

  • Computer color systems use light to portray color, so RGB is Red, Green, and Blue light. This system is also known as additive color mixing, so remember that when you turn on the light, you add color to the computer design process.
  • Print color systems don’t use light, so CMYK stands for four colors of ink: Cyan, Magenta, Yellow, and Kryptonite (just kidding!). The “K” stands for “Key,” or the black ink that printers use to create values to a true black on paper. Since these inks are added to a piece of paper rather than to a backlit computer screen, the use of this system is known as subtractive color mixing.

Another way to remember the difference between the two systems:

  • When RGB lights are mixed together, they create white light (additive).
  • On the other hand, when CMYK inks (or paints) are mixed together, they create black ink (subtractive).

Unfortunately, a simple way to convert RGB to CMYK or from CMYK to RGB is unknown. The best the designer can hope for is to use a color management system that uses color profiles that can describe the spaces that are being converted. The conversions will never be exact. This is why it’s always good to design print materials with CMYK systems and images from the beginning, and why it’s good to always use RGB systems and images for Web design from start to finish.

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