Trichromatic theory of colour vision.—The measurement of retinal fatigue

Abstract

That fatigue of the retina by a colour will change the hue of the spectrum colours is well known. In this paper a method of measuring the amount of fatigue is described, showing that by fatiguing the retina colour-blindness is produced which is the same as that found when one of the three sensations is deficient in sensitiveness. In the first part of this communication the fatigue is produced in one eye, and the change in hue is registered by the unfatigued eye, and from these observations what we may call the factor of the fatigue is calculated, which is the ratio in sensitiveness of the unfatigued sensation to that of the fatigued. In the second part of the communication a method is described of measuring the luminosity of what, for short, we will call the fatigue spectrum, which is, of course, the luminosity of the spectrum as seen by the fatigued eye. In previous papers the value of the three sensations in luminosity to the normal eye has been given, and the red, green, and blue sensations have been indicated in equations as R. S., G. S., and B. S. In this paper the luminosities of the three sensations of the spectrum have to be shown as curves of equal stimulation, and the percentage values of the different colours have been derived from these curves. The curves of equal stimulation of the spectrum are the ordinary sensation curves, two of which (the blue and the green) have to be multiplied by factors to make them of equal area. Equal ordinates in these curves will then give the amount of white light existing in the different colours. The sensations of equal stimulus are indicated for the sake of brevity as R’S., G’S., and B’S.