ARTIFICIAL DAYLIGHT.

Wanganui Herald, Volume LIII, Issue 16038, 31 January 1920, Page 10

ARTIFICIAL DAYLIGHT.

A REMARKABLE INTENTION

(Age Correspondent.) LONDON, November 27

Everyone knows that it is impossible to judge colours at night under artificial light, because under such conditions the colours look diffeirent to what they do in daylight. The scientific reason for this difference ia that white light is a mixture of all the colours of the spectrum, and in artificial light the red and yellow rays of the spectrum are more pronounced than the violet and bine rays. In daylight the violet and blue rays have more energy than in artificial ligfit, because the incandescent gases of the sun which produce daylight give out a much higher temperature than can be produced by artificial light. Moreover, when daylight comes through a window the rays, scattered from millions of particles, lose more of their red and yellow components than of the violet, and blue.

Mr George Sheringham, an English artist, recently sot himself the task of producing an artificial light similar to daylight, by increasing the strength of the violet and blue rays in comparison with the red and yellow. His object was to produce a light which would enable him to judge colour’s accurately, and so continue at night his work aa a painter, and also on foggy days when there is no real daylight. He succeeded in his task, and is arranging a public exhibition of his pictures painted under artificial light. It was not until his successful experiment became known to some meen of scientific attainments that he was told that his invention is of considerable value to industry, especially _in a country like England, where in the middle of winter there are only seven or eight hours of daylight on clear days, and where frequent fogs render it necessary to work under artificial light all day. This new invention will be valuable in all industries where it is necessary to judge colours accurately, such as the dyeing and textile trades, colour printing, photographic reproduction in colour, tea blending, tobacco blending, illuminating shop windows, studio work, and exhibiting paintings by night. One manufacturer I whose employees have po maich^artalMaal

dyes states that the invention will be of great assitaneo to him, as under present conditions his employees have often to cease work at 2 p.m. in winter, because after that hour the light is so poor that it is impossible to distinguish colours clearly. Mr L. C. Mar tain, of the optical engineering department ox the Imperial College of Science and Technology, and Major A. Klien, of the experimental department of the Camouflage School established during the war, have been assisting Mr Sheringham in the perfection of his invention, and a demonstration of its working was given by Mr Martin at a meeting of the Royal Society of Arts. The apparatus consists of a high-power electric light bulb, Ittcd with a cup-shaped opaque reflector, the silvered inner side of which reflects a light against a parasol-shaped screen placed above the light. The screen is lined with small patches of different colours, arranged according to a formula worked out by Mr Sheringham, and carefully tested and Tier fee ted in the laboratory of the Imperial College. The light thrown down from the screen shows colours almost as well as in full daylight, and much better than under any other arrangement of artificial light. Tests were made successively with daylight, ordinary electric light, and the Sheringham light. Under the latter delicate yellows were quite distinct, indigo blues were blue, cobalts had their full value, and violets lost the reddish shade which they display in electric light.

In the Sheringham light the whole of the rays are scattered and diffused bef’-re being thrown on the coloured objects. The effect of the pigments in the reflector is to absorb a relatively greater proportion of the components towards the red end of the spectrum, so that the light approximates to the condition of daylight. In the process a proportion of the illuminating power of the light ia naturally lost.