Light colour and object colour
Fundamentals of colour perception
The colour perception of people depends on the light spectrum and colour of the reflecting material
White light on white objects
Objects becomes visible when light falling on them is reflected into our eyes. With sufficient illumination we therefore not only recognise their form but also their colour. The physical trigger for this colour sensation is termed the colour stimulus. Its composition depends on the spectral distribution of the light source as well as the colour and surface characteristics of the material. A surface reflecting all the visible spectral ranges appears white to us.
White light on coloured objects
If white light falls onto a material with a red surface, the wavelengths of the red spectral range are reflected by the material and all others are absorbed. We process this stimulus to create a colour sensation that we call red. We can detect nuances in colour with white light with a continuous spectrum.
Coloured light on white objects
Materials can only reflect those wavelengths contained in the spectrum of the illuminant. The spectral ranges contained in the light are mixed on white surfaces. The colour sensation corresponds to the mixed colour of the reflected light.
Coloured light on coloured objects
Any wavelengths missing in the light spectrum cannot be reflected. This means that information about the colour of an object can no longer be communicated in such situations. Delineating the colour nuances of a painting for example requires white light with a continuous spectrum. Only in this way is it possible to achieve the authentic visual experience of the colours.
