A distinction is made between additive and subtractive colour systems. Subtractive colours arise through the light share which a surface absorbs or reflects. Depending on the colour of a surface, different portions from the colour spectrum are absorbed and correspondingly not reproduced. The extremes form black and white surfaces, which reflect hardly any light (black) or the entire colour spectrum (white). All subtractive colours can be mixed out of yellow, magenta and cyan. They are the basis of the CMYK colour model, which is used in printing. Additive colours (right image) are created through the superimposition of coloured light. Different colours can be produced depending on the composition of the red, green and blue (RGB) colour sections. If the three RGB colours are projected on each other in equal maximum shares, white is created. All devices such as monitors (self-illuminating) or scanners and digital cameras work with the RGB model.