Lightness and Brightness and Other Confusions

each apple. We see that the farthest apple is the same colour as the other two,
even though it is in shadow while the other two are in stronger light. We see
that all the apples are (approximately) spherical, although one apple is occluded
by another so that only a part of it is visible. We also see that the apples
are all the same size, although the retinal image of the farthest apple is
smaller than that of the nearest one. However, due to the visual phenomenon
of constancy scaling, they are seen to be more similar in size than they would
be in a photograph or classical perspective image of the same scene.
Figure 4. Two interpretations of the same three apples.
(Images: Harald Arnkil)
The above scene could be translated into a flat image in several ways 40 , revealing
the multiple levels of seeing. One artist might concentrate on the
apples’ chromatic differences in the lights, highlights and shadows, another
one might ignore them and depict them as uniform green. A photorealist
would make a careful note of the optic size difference. Another artist might
paint all three apples the same size in accordance with constancy scaling and
knowledge of the apples’ physical similarity. And so on. All depictions would
be correct and accurate in their own way, but if displayed side by side in an
exhibition, they would appear strikingly different. Viewers, who were familiar
with the original scene, might be surprised (or delighted) by the different
‘interpretations’. They might find that they have missed out on something
that one of the artists has emphasized or made apparent. Like artists of a
given school, we are all – to a certain degree – ‘trained’ to notice and to see
particular aspects of our visual environment. This occurs mainly through
shifts of focus and attention that are directed by our intentions. A botanist
might be trained to notice minute variations of colour in greenery or a fisherman
to forecast the weather from a combination of colours and forms in
sky, clouds and water. But it is highly unlikely that the Ukiyo-e -artists of 18 th
– 19 th Century Japan did not see shadows or the converging optical effects of
40 The idea, developed during the Renaissance and after, that the perspective image is
the ultimate scientific interpretation of space, is of course based on the idea of a ‘retinal
image’. Translating space experience into a flat image by using perspective was then a
task of figuring out how that retinal image is created – a matter of optical science. (See
Kemp 1990).
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