Colour-blindness and colour-perception / by F.W. Edridge-Green.

  • Fredrick William Edridge-Green
Date:
1909
Catalogue details

Licence: In copyright

Credit: Colour-blindness and colour-perception / by F.W. Edridge-Green. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    minor objections of the colours having different degrees of luminosity, arrangement of threads, etc. Stilling's lithographed plates have the additional objec- tion of having the twin colour overlapping the ground. 5. Tests in which the Complementary Colour has a Part.—Shadows coloured by contrast, Cohn's chromasciop- ticon, Waldstein's chromatoscope, and Phliiger's test come under this head. Tests of this description have very little value; they are more likely to detect the ignorant than the colour- blind. The colour-sense is diminished in the colour-blind, but not to such a degree as to prevent them from seeing complementary colours. 6. Quantitative Tests for Colour-blindness.—In Chapter XI. I have discussed the methods of ascertaining quanti- tatively the degree of colour-blindness. It now remains for me to deal with those tests which have been con- tracted upon the theory that the various degrees of colour- blindness are only varying degrees of certain defects. In the case of the Young-Helmholtz theory, varying degrees of red-blindness, green-blindness, or violet-blindness. I have shown that there are several causes which go to make up the total defect which is evident as colour- blindness. Shortening of the red end of the spectrum interferes very considerably with the perception of red at a distance; but diminution in psycho-physical perception has comparatively little effect upon the perception of colours at a distance. I have several times examined persons belonging to the class of the three-unit with an unshortened spectrum, and found that they were able to recognize red and green at the normal distance. It seems to me that, until the various causes which give rise to defects of colour-perception are definitely recog- nized, no efficient quantitative tests can be constructed.
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