Stiles’s π5 field sensitivity approaches the sensitivity of the long-wavelength (L) cone as the duration of the test flash decreases. Further, for short test flashes mixtures of red and green backgrounds are additive. For long test flashes the backgrounds cancel, the mixture raising threshold less than expected. These results are explained if π5 is approximately the L-cone sensitivity combined with some opponent-channel sensitivity.
© 1981 Optical Society of America
Carl R. Ingling, Jr. and Eugenio Martinez, "Stiles’s π5 mechanism: failure to show univariance is caused by opponent-channel input," J. Opt. Soc. Am. 71, 1134-1137 (1981)