The colour depth indicates the maximum number of colours that can be displayed (for example on digital cameras, monitors or printers). The number of possible colour gradations is given in bits.
An image is composed by the arrangement of pixels in a raster graphic. Pixels contain information about colour and brightness levels, whereby these are usually determined by three colour channels with the colours red, blue and green. By additive mixing of these three basic colours, any desired colour can be created.
The more colour gradations the individual colour channels can assume, the more colours can be represented in total. The unit of measurement bit indicates how many colour gradations are possible within a colour channel. Each bit can only register 2 colour gradations, so the number of possible colours doubles with each bit.
An example: a camera that has a colour depth of 4 bits can capture and display 16 gradations (24 = 16) within a colour channel. Thus, since each colour is composed of the three colour channels red, blue and green, a total of 12 bits, i.e. 4096 colours (163 = 4096) can be represented. A colour depth of 8 bits per colour channel (i.e. a total of 24 bits) results in 256 gradations (28) per colour tone and over 16 million possible colours.
Most cameras have a colour depth of 8 bits per colour channel (24 bits in total). From this number of possible colours onwards, we also speak of true colours, as the colours appear very real and natural. In the meantime, there are also cameras on the market with which 10, 12 or 14 bits per colour channel are possible. In the case of 14 bits, this corresponds to over 4 trillion colours. For post editing of pictures this can be very interesting, but for normal use 8 bits are completely sufficient as the quality of the pictures does not improve significantly, especially since the human eye can only distinguish about 200 colour tones.