PHENOMENA OF COLOUR

Press, Volume LXIX, Issue 21024, 28 November 1933, Page 15

PHENOMENA OF COLOUR

I'ROFESSOK UAIiDANPrS |] THEORY , i i THE EYE OF THE BEHOLDER |s i' LONDON, October lfi. j, The glorious colours of sunset arc not "really there.'" They are faked, , so to speak, by the human eye itself in an elVort to make the sunset conform -to the colour-balance in the field ' of vision which the eye all through life strives to establish. Such would be a crude and partial expression of a revolutionary theory of vision put forward by Professor .1. S. Ilalcki.ie, one of the most brilliant and daring physiologists living, in an inaugural address yesterday 1o the one hundred and ninety-seventh session of the Edinburgh Royal Medical | Society. j 1 If his theory is true, Professor Hal'dane claimed, the assumption on 'which Galileo and Newton founded j physics, that "our sense-organs are simply receptive of various kinds of impressions from a surrounding j ,'physical world," .'loo.- not cover the ! fads-as Uerkcley. the philosopher, I long ago claimed. lie would try to I show that "the actively maintained j organic unity which we call life" affects what we ;:ee as completely as it affects growth or respiration. "A gigantic 'petitio principii'—a begging of the Question—was involved in Galileo's separation of subjective from objective." Yellow IMurte Blue. Newton, in his Optiks, had assumed that the colour of any light depended solely on its refrangibility, or "wave-length," The professor proceeded to show to the audience that he could make light which by all the laws of physics ought to be yellow turn blue, white, green, red, or any other colour—just by changing the whole of its background. A small area of a white screen lit by a white daylight lamp, for instance, went blue in the darkened hall when seen through a hole in another white screen lit by ordinary electric light [ (which is very yellow), and green when the yellow light was replaced by a red one. The front screen, after a few moments, continued to look white, though it ought, physically, to . be red; and the back visible patch of the screen, lit by a much whiter lamp, ' was vividly coloured. i To explain these extraordinary rei suits of "simultaneous contrast," first noticed by Rumford more than a century ago, and since largely overlooked, the' professor put forward an entirely new theory. lie declared: (1) In the perception of either colour or brightness our vision, as a whole, is always active; there is no merely objective cause of colour or brightness. (2) In this active perception we can distinguish the co-ordinated maintenance of colour and complementary colour, as well as brightness and darkness, in the field of vision. Developing the theme by many more exoeriments, he showed that this coordinated maintenance of colour "can be predicted on the assumption that the whole illumination (of the field of ' vision) is being more easily adjusted actively towards the co-ordinated combination of colour and complementary colour which together appear as white"—even though this apparent white might physically be "not white at all." While Sky. Thus the back screen, seen through a hole in the front screen, had been deficient in yellow, as far as the comfort of the eye was concerned, because the greater part of the field of vision was lit by a yellower light, and so it turned and stayed blue. To eliminate the colouring of the 1 field of vision in order to discover what ; colour objects appear when they com- • mand the eye's whole attention, one could look at them through a narrow,! ' blackened tube, shutting out the rest; I of the world. . , Then, Professor Haldane claimed, the sky went white—its familiar blue ■, being merely imposed by the eye to, balance the brilliant yellow rays of | the sun; purple went pink, the clouds ; 1 were seen to be yellow, and the c<>l- - ours of .sunset were found to be I tawdry, owing their apparent glory to ; i | the eye's activity in balancing its total I I] illumination towards while. j