Dark adaptation of the long-wavelength sensitive cones.

Long-wavelength sensitive (L) cone dark adaptation curves were measured with a 10-msec, 20' v.a., 650 nm test flash and a moderate intensity adapting field. When the 650 nm and 500 nm fields were equated for the L cones, the dark adaptation curve fell faster for the 500 nm field than for the 650 nm field. Over the range of adapting lights used, no adjustment of the intensities of the two fields made their dark adaptation curves similar. When 500 nm light was added to the 650 nm field, dark adaptation was faster. Visual sensitivity is not regulated by any single photoreceptor type in this experiment.