Psychophysical studies of interactions between luminance and chromatic information in human vision
Abstract
In this thesis, I investigated how human vision processes colour and
luminance information to enable perception of our environment. I first
tested how colour can alter the perception of depth from shading. A
luminance variation can be interpreted as either variation of
reflectance (patterning) or variation of shape. The process of
shape-from-shading interprets luminance variation as changes in the
shape of the object (e.g. the shading on an object might elicit the
perception of curvature). The addition of colour variation is known to
modify this shape-from-shading processing. In the experiments presented
here I tested how luminance driven percepts can be modified by colour.
My first series of experiments confirmed that depth is modulated by
colour. I explored a larger number of participants than previously
tested. Contrary to previous studies, a wide repertoire of behaviour was
found; participants experienced variously more depth, or less depth, or
no difference. I hypothesised that the colour modulation effect might
be due to a low-level contrast modulation of luminance by colour, rather
than a higher-level depth effect. In a second series of experiments, I
therefore tested how the perceived contrast of a luminance target can be
affected by the presence of an orthogonal mask. I found that colour had
a range of effects on the perception of luminance, again dependant on
the participants. Luminance also had a similar wide range of effects on
the perceived contrast of luminance targets. This showed that, at
supra-threshold levels, a luminance target’s contrast can be modulated
by a component of another orientation (colour or luminance defined). The
effects of luminance and colour were not following a particular rule. In
a third series of experiments, I explored this interaction at detection
levels of contrast. I showed cross-interaction between luminance target
and mask but no effects of a colour mask.
Type
Thesis, PhD Doctor of Philosophy
Rights
Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
http://creativecommons.org/licenses/by-nc-nd/4.0/
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