Lightness and Brightness and Other Confusions

parallel lines although they almost entirely excluded shadow and linear perspective
in their pictures.
Seeing as a visual process
Visual perception is often described as a linear process that starts with the
stimuli of the outside world and ends in perception and experience. This
process involves several parallel paths of neural activity. Various aspects of
visual information, such as shape, movement, size, orientation and colour,
are treated by separate processes that connect and interact with each other.
Although many advances have been made in the study of the individual neural
processes and specialized brain areas, it is still not known how the separate
processes are integrated into a coherent visual experience. E. Bruce
Goldstein has outlined the visual process in Sensation and Perception (Goldstein,
1999) with the following chart:
Proximal
stimulus
Transduction Processing Perception Recognition Action
Figure 5. The visual process (Goldstein, 1999)
Paraphrasing Goldstein, the stages (for vision) could be further described as
follows:
Distal stimulus = object or surface or light source outside the observer.
Proximal stimulus = pattern of radiant energy on the retina(s) caused by electromagnetic
radiation from the distal stimulus. “The radiation energy that reaches and
manages to activate the receptors in the eye’s retina”. (Hård and Svedmyr 1995, p
218, translated from Swedish)
Transduction = transformation of the above radiant energy to electrical signals in
the retina.
Processing = the processing of the electrical signals in neural networks and pathways
in the retina and brain.
Perception = the mental process of synthesising the signals into percepts as a result
of an interaction of higher and lower brain levels in a parallel and multilinear processes
(bottom up and top down processing).
Recognition = the cognitive process of conscious or unconscious interpreting of the
percepts according to meaningfulness and familiarity.
Action = conscious or unconscious reaction to perception and recognition.
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