The discrimination of colour / by F.W. Edridge-Green ; (communicated by W.M. Bayliss).

  • Edridge-Green, F. W. (Frederick William), 1863-1953.
Date:
1911
Catalogue details

Licence: In copyright

Credit: The discrimination of colour / by F.W. Edridge-Green ; (communicated by W.M. Bayliss). 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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    Dr. F. W. Edridge-Green. [-A-pr. 24 chromatic region. I have magnified the image of this region with eyepiece, of different power, making a corresponding increase in the light to make u for the loss of luminosity caused by the magnification. I have also oi>struot§i the central portion of the monochromatic region with a screen, and tb remaining portions have still appeared monochromatic. The most conclusiw experiment, however, is the examination of the monochromatic region wit an achromatic double image prism, the intensity of the source of light beim increased as before. By this method two rectangular monochromatic fiek are seen, and can be arranged so that they are side by side and just touci The portion belonging to the red side of the spectrum of one can be made.-1 touch the portion belonging to the violet side of the spectrum of the othe j This position is therefore most favourable for the detection of any differei^ and yet I cannot detect any, neither can any other observer to whom I ha' | shown the experiment. The experiment can be observed objectively in tl i following manner: An arc light being used for the illuminating sourci a pure spectrum is obtained; a portion of this spectx’um, forming a luon chromatic region, is allowed to pass through an adjustable slit. Two iiuag,' of this monochromatic region can be thrown with the aid of a double imaj prism upon a screen and made of any' required size. The varying size of tl monochromatic regions with different persons can by this means be deprpi strated to a large number. I Another point which I found with Lord Eayleigh’s apparatus is t difficulty of obtaining both fields of similar intensity. The slighfi movement of the eye also causes an alteration in the number and ki).j of rays which enter the eye. When tw'o fields are of unequal intensi^l the physiological effect of contrast is evoked, which causes an erroneo judgment of the colours under observation. In fact, weak orange light m! by contrast with bright red light, appear green. In making experiments the discrimination of colour, the rays of light from the two regions to compared should strike the eye at as nearly as possible the same angle; t fixation point of the ey'e should be in the centre between the two region8,«^ that one region may not be more influenced by the pigment of the yell j spot, or the blood in the retina, than the other; and equal amounts of lif'j from each region should enter the eye. l! The importance of the irregularly dispersed light in association w l contrast in dealing with questions of colour has been overlooked by ma ' physicists, as several instruments have been constructed for the investigat. j of colour and colour-vision, which are defective on this ground. It was t j irregularly dispersed light, as shown by Helmholtz,* which caused the appan j ^ * ‘ PoggendortPs Annalen,’ 1852, No. 8.