Lightness and Brightness and Other Confusions

uniformly coloured. Colour variations are defined as the local appearances
of the identity colour. These differences might depend on light
distribution, reflections from other surfaces and contrast effects. (Billger
1999, p 11).
By changing our mode of attention we are able to, as it were, separate the
various layers or spatial attributes of perception. This shifting of attention
between local and global or between object, light and shadow, is a part of the
normal working methods of any visual artist. The difference between the
reflective attentions of an artist or visual researcher and those of the ‘man in
the street’ is one of level of consciousness. According to Billger the perceived
colour of material is subject to a certain elasticity, due to the aforementioned
spatial factors. This elasticity is an important subject in Billger’s study, where
a method to ascertain and record the influence of different spectral distributions
of ambient light is at the centre of attention. Neither nominal colour nor
identity colour claims to represent ‘the real colour of the object’. The important
difference between the two concepts is that nominal colour can be measured
by comparison to a colour sample, whereas identity colour cannot be
measured or operationally determined in any way, only perceived through
holistic reflective attention.
Figure 21. The three apples as ‘seen’ by a camera. (Photo: Harald Arnkil)
Constancy colour
If we accept that the world is coloured in some way, but dismiss the view of
colour physicalism that objects’ colours are the same thing as their spectral
reflectance properties, we must look somewhere else for the ‘real’ colour (if,
indeed, there is such a thing as ‘real’ colour). Hård’s definition of inherent
colour, “… the colour that one imagines as belonging to a surface or a material,
irrespective of the prevailing light and viewing conditions”, is reminiscent
of Helmholtz’s idea of colour constancy as a mechanism or ability in
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