Researches in colour vision : and the trichromatic theory / by William de W. Abney.
- Abney, William de Wiveleslie, Sir, 1843-1920.
- Date:
- 1913
Licence: In copyright
Credit: Researches in colour vision : and the trichromatic theory / by William de W. Abney. Source: Wellcome Collection.
Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)
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![of the atmosphere were met with, as the conditions were all in favour of the colour blind and defective form vision examinees.] Test by Simultaneous Contrast. Another instructive test is founded on the answers given as to the colours found by the simultaneous contrast between white and the different colours of the spectrum. The contrasts which the colour blind see appear often to be extraordinary, but when considered in the light of the three-sensation theory they lose what may be called their extravagance. The smaller the factor of the defi- cient sensation, the more divergent from the normal do the contrast colours of the white become. It is no uncommon answer, for instance, when to the normal eye a colour is green and the white is a salmon colour that both stripes should be called green. The mistakes made very readily indicate the nature and extent of the colour blindness that is being examined. This, of course, is only a qualitative test. As an example of the mis- takes that may be made, the following contrasts were observed by an eye which had only *5 of the normal green sensation :— Colour shown. Normal Contrast of White. Colour to Colour Blind. Contrast of White to Colour Blind. Dark red Brighter red Orange Greenish yellow Pale green Pure green Bluish green Greenish blue Green-grey Green-grey Blue Umber colour Lavendar Pink Salmon Yellow Green Red Green Pale green Green Blue-green Dark green Blue Red Pale green Green Blue Red Red Pale red Green](https://iiif.wellcomecollection.org/image/b21287739_0439.jp2/full/800%2C/0/default.jpg)
