Lightness and Brightness and Other Confusions
Lightness and Brightness and Other Confusions
Lightness and Brightness and Other Confusions
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Especially problematic is the situation where one <strong>and</strong> the same word is given<br />
alternative conceptual definitions, while having also a more or less established<br />
everyday usage. Take for example saturation. Even if each of the definitions<br />
is clear, it is very confusing that one <strong>and</strong> the same term can have so<br />
many slightly varying definitions.<br />
There are also generic words <strong>and</strong> terms that have been given very specific<br />
meanings within a given scientific discourse. These can be misunderstood or<br />
confused with their more generic meanings outside that discourse. Examples<br />
of this are the terms inherent colour <strong>and</strong> identity colour. Within the conceptual<br />
framework of their discourse these terms are well defined (<strong>and</strong> thus useful),<br />
but considered out of that framework they can be very confusing.<br />
Colour identification through three properties<br />
Irrespective of the starting point, be it physical, psychophysical or perceptual,<br />
any single colour can be described <strong>and</strong> identified through three independent<br />
properties. This makes it possible to organise <strong>and</strong> examine all possible<br />
colours within a three-dimensional conceptual structure, called a colour<br />
space. There exists, however, some variation between systems as to which<br />
exact visual properties constitute the three parameters of colour – <strong>and</strong> even<br />
more disagreement about how these parameters are defined. The end result is<br />
that there are in use today several colour systems exhibiting various ideas of<br />
colour.<br />
It is relatively easy to build a model of colour from three variables such hue,<br />
lightness <strong>and</strong> saturation. The three dimensions lend themselves easily to a<br />
variety of geometric shapes. These colourful cubes, cylinders, spheres, cones,<br />
double cones, tetra- <strong>and</strong> octahedrons <strong>and</strong> their more complex asymmetrical<br />
variations may look convincing <strong>and</strong> beguilingly attractive as models for the<br />
parameters of colour. However, if colour is to be understood as something<br />
that is neither a property of objects nor entirely of the perceiver – but as<br />
something that happens in the dynamic interaction of the two – then no static<br />
geometric model could ever describe it.<br />
Many, but not all, colour systems include lightness as one of its variables.<br />
Sometimes other words are used to denote basically the same thing. In the<br />
Munsell system, for example, the darkness–lightness variable is called value.<br />
<strong>Lightness</strong> or value typically forms a scale between maximum blackness <strong>and</strong><br />
maximum whiteness. Although it is a basic variable it is not defined the same<br />
way in all systems. One system might define lightness in photometric terms,<br />
another with reference to st<strong>and</strong>ard samples. This <strong>and</strong> the conceptual confusion<br />
between lightness <strong>and</strong> brightness, is one of the topics of this article.<br />
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