Everyone concerned with the accounts given by eyewitnesses of the colour of objects they have seen should be aware of the effects of the conditions of illumination on the descriptions of colour that are given. A common example is the change in colour rendering brought about by sodium vapour street lighting. The exact colour of light-coloured vehicles, which offer no difficulty in daylight, becomes exceedingly difficult to determine and describe at night under either sodium or mercury vapour lamps.
This scholarly book is concerned in great detail with the spectral energy distributions of daylight and artificial light sources which are one of the principal factors in determining the colours of objects we see. I t ranges from the speculations of Greek philosophers on the nature of colour and light to recent measurements of solar energy distributions made from high altitude balloons.
Whilst it is difficult to imagine criminal cases in which such detailed considerations of the effect of light on perceived colour might be necessary, this is by no means so in civil cases where, for example, the closeness of a colour match in a manufacturing process might be in dispute. But perhaps one lesson soon learnt in criminal matters is that the unexpected turns up sooner or later. Be that as it may, this book is likely to be the standard work on light sources, both natural and artiticial, and their effects on colour for a long time to come. D. Patterson.