The relation of light perception to colour perception / by F.W. Edridge-Green.

  • Edridge-Green, F. W. (Frederick William), 1863-1953.
Date:
1910
Catalogue details

Licence: In copyright

Credit: The relation of light perception to colour perception / by F.W. Edridge-Green. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    if we subtract the rays occupying the missing portion from the colour of confusion. For instance, if we take a blue and a pink which have been put together as identical by a person with a shortened red end of the spectrum, and look at them through a glass which is opaque to the red but transparent to the remaining rays of the spectrum, both will appear alike in hue and shade. A person with considerable shortening of the red end of the spectrum will look at a red light (which is so dazzlingly bright to a normal-sighted person as to make his eyes ache after looking at it closely for a few seconds), at a distance of a few inches, and remark that there is nothing visible, and that the whole is absolutely black. It is obvious that the light must consist only of rays occupying the missing portion of the spectrum. | The same remarks which I have made for a shortened spectrum apply to cases in which there is defect of light perception through absorption or any other cause. The person having the defect is placed in a similar position to a normal-sighted person with those particular rays removed or reduced to the same intensity. I Another effect of shortening of the spectrum when it is sufficient to interfere with the difference perception which appears to be inherent in the bentral nervous system is that the colours appear to be moved in the direction of the unshortened portion. For instance, we find the neutral point of the dichromic with shortening of the red end of the spectrum further towards the violet end of the spectrum in comparison with a case in [which the spectrum is of normal length. In the same way a trichromic with la shortened red end of the spectrum has the junction of the red and green 'nearer the violet end than in a case where there is no shortening. ’ The point that I specially wish to emphasise is that, though every case in which there is defective light perception can be explained by a defective sensibility to light of certain wave-length, not a single case of the very large number of persons that I have examined can be explained on the [older theories, that is, the defect of light perception cannot be explained on the assumption that there is a defect in a light-perceiving substance which is sensitive to rays of light from a considerable range of the spectrum. 2. Cases in which there is Defective Colour Perception. Even in cases where there is actual colour blindness or deficiency of hue perception it is equally important to differentiate between the perception of light and the perception of hue. Let us take as example a case which at first sight appears to be in support of the older theories, a case of so-called red-blindness, in which there is dichromic vision with considerable shortening of the red end of the spectrum. It can be easily shown that the defect b 2