Lightness and Brightness and Other Confusions

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Equal NCS chromaticness (c)
Equal NCS whiteness (w)
Equal NCS blackness (s)
Figure 16. Chromaticness, blackness and whiteness in the NCS system
Brightness has an indirect, non-linear correlation with luminance; it is a
perceived quantity that cannot be instrumentally measured. For example the
full moon can be bright and luminous – almost dazzling – at night, but
viewed in the very different global setting of daylight (this is sometimes possible)
it will look only pale, a mere ghost of its nocturnal appearance, although
its measured luminance will be the same as at night. The difference in
the mode of appearance and the experience of brightness is, of course, due to
adaptation and contrast – and this is exactly how brightness differs from both
lightness and luminance.
One speaks of the sun, the moon or a lamp as being bright, but of a table or
room as being brightly lit or illuminated (it is idiomatic in English, though, to
speak of a room or a landscape filled with daylight as being bright). There are
instances where the two modes of experience merge, as in self -luminous
objects or surfaces in darkness being illuminated by cropped beams of light
with for example theatrical profile projectors (which can lead to an illusion of
self-luminance). Various types of image projection (slide-, overhead-, film-
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