CL600 colour measurement systems

Tristimulus colorimetry started in the nineteenth century. Young discovered the fact that the eyes were susceptible to three colours, red, green and blue and Clark Maxwell did experiments based on the mixing of red, green and blue colours to try and simulate the effects on the eye of any other colour. The result, in tristimulus values, where X represents red, Y represents green and Z represents the proportion of blue with regard to their respective saturations, provided a series of numbers which were additive only. These values, although they are used currently, are very difficult to establish meaningful colour difference work. The addition of two colours results in modifications to the X, Y and Z values of both of the colours, i.e. they progressively increase and do not decrease.