In search of the elusive long-wave fundamental.

Action spectra for threshold detection of flicker (30 Hz) were obtained on 11 deuteranopes under carefully controlled adaptation conditions. Individual differences were large, so that each one of the long-wave fundamentals proposed by different theorists finds reasonable justification in the spectrum measured on at least one deuteranope. Some deuteranopes' spectra are not described by any one of these "fundamentals". To a first approximation at least, trichromats' spectra show the property of linear additivity. One such trichromat's spectrum agreed well with that of a deuteranope with whom he shares a common erythrolabe, and appears to be uninfluenced by his chlorolabe-filled cones.