Biology Reference
In-Depth Information
14
Further exploration of
chromatic rod vision
14.1 C of n t r i b u t i of n of f J . J . M c C a n n
and J. L. Benton
Soon after the discovery that rod signals may initiate all kinds of hue,
a number of research workers contributed to the further exploration
of this phenomenon.
Firstly, McCann and Benton (
1969
) convincingly demonstrated
that rods had the ability to interact with the long-wave cones (L-cones)
and thereby produce a multicoloured image. This was illustrated by
first illuminating a multicoloured paper with a 656 nm monochro-
matic light at an intensity level just above the colour threshold
in order to activate only the L-cone mechanism. Thereafter, they
superimposed a monochromatic light of 546 or 450 nm that activated
only the rod receptor system. Adding the scotopic light dramatically
changed the colour of the display; red, orange, yellow, blue-green,
brown, grey and black could be seen in the display.
A more sophisticated and detailed study of this rod-cone
interaction colour effect was later reported by McKee, McCann and
Benton (
1977
). To produce the multicoloured display, a transparent
photographic picture was taken both through a red and a green filter and
then combined. The display was then illuminated with a red 656 nm
monochromatic light at an intensity just above the colour threshold
and by one of ten monochromatic lights selected from the 420-600 nm
region of the spectrum. By increasing, in turn, the intensity level of
each of the ten monochromatic lights they demonstrated that the
threshold level of the multicoloured image (i.e. the lowest intensity
level where the observer reported that he could see a faint image of red,
yellow and blue-green) fitted the scotopic luminosity curve.
