What is the CIE system of colorimetry?
A. Colour is the sensation achieved when light falls on the retina of the eye. In the retina colour sensitive receptors are ‘triggered’ to produce electro-chemical signals, which are sent to the brain to produce the sensation of colour. The light reaching the eye is the product of the light reflected at each wavelength by the sample and that of the illumination source shining on it. The three types of receptor each peak in sensitivity at different wavelengths – one at short wavelengths, one medium wavelengths and one at slightly longer wavelengths. This means that any colour can be reproduced by just 3 coloured dyes, pigments or coloured luminous stimuli – so long as their peak absorption or emission wavelengths are also separated. It also means that colours can be seen to match despite having different spectral composition – a phenomenon known as metamerism. Such a match will generally fail when the light source shining on the sample is changed. Colour (whether coloured light or print
