The additive RGB colour model is used in colour monitors and other auto-lighting systems as well as in scanners and digital cameras. RGB colours are created by mixing coloured light. RGB (red, green and blue) represent the three primary colours red, green and blue here. A hue can be defined precisely through individual share of these colours, insofar as a specific RGB is given. The usual ones are e.g. Adobe-RGB, ECI-RGB, sRGB. These RGB colour spaces are also distinguished by the size of the colour spaces, so e.g. ECI-RGB is approximately 60 percent bigger than sRGB. Each colour share can vary between 0 and 255. Given equal shares of red, green and blue a colour of between white and black is produced depending on the value. If two of the basic colours are mixed by equal amounts, the fundamental colours of the subtractive CMYK colour model are produced.