CONTRIBUTION OF J. J. MCCANN 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 monochromatic 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.