Colour mode

The colour mode is a setting that determines the depth to which colours can be displayed in an image file. This also affects the size of the file.

The most common colour modes are:

  • RGB mode (millions of colours)
  • CMYK mode (colours for four-colour printing)
  • Lab/CIELab
  • Index mode (256 colours)
  • Grayscale (256 shades)
  • Bitmap (2 colours: Black or white)


RGB stands for red, green and blue. Human colour vision is based on these colours.

Computer monitors and televisions each have red, green and blue light-emitting areas. If all three colours are turned on, we see white light. If all three colours are turned off, we see black.

The RGB colour system is based on additive colour mixing and used for self-luminous systems like monitors, etc..


sRGB is the most widely used RGB colour space, and was created for monitors by Hewlett-Packard and Microsoft in 1996. sRGB is the standard colour space of all inexpensive digital cameras and scanners. Nearly every 8-bit RGB file without profile identification corresponds to sRGB.

Intel, Pantone, Corel and numerous other companies rely on sRGB or have implemented the colour space as standard. Today sRGB is no longer popular in the printing industry, as the colour space is sometimes much smaller than the printable colour range of ISOCoatedV2 and therefore partially restricts the printable colours. Colour spaces such as AdobeRGB 1998 or ECI-RGB V2, which are optimized for printing, are therefore also preferred today for image processing in RGB.

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