No_6_December__1938_and_January__1939 — Page 13

Hong Kong Builder

17

HOME LIGHTING

FULL

In shade of tree 1,000 foot candles.

FOREWORD

of

In shade porch 500 foot condies.

Electricity has become so much cheaper during the last few years that really efficient utility lighting is now within the reach of every householder, whilst lighting for purely decorative purposes need no longer be regarded as a luxury but a necessary adjunct to the well-equipped

home.

It is estimated that we spend half our waking hours under artificial lighting, and as this artificial light is often a very small fraction of natural daylight, it is not surprising to find that a large number of us have defec- tive eyesight.

DAYLIGHT AND ARTIFICIAL LIGHT

The eye may be likened to a wireless receiving set with automatic tuning for the reception of visible light rays. We are able to see objects by virtue of the light reflected from them, and also as a result of colour con- trast due to the eye being able to discriminate between the different wavelengths of light. On a clear midsum- mer day, the illumination out in the open is roughly 10,000 foot-candles or degrees of illumination. It is possible to read in absolute comfort under the shade of a tree on a sunny day where the illumination may be

In sun 10,000 foot candles.

just inside

window 200 foot candles.

about 1,000 foot-candles. If we consider the daylight values indoors, the illumination near a window is often a few hundred foot-candles, and though this value drops off rapidly as we move away from the window, the light in the farthest corner of the room in daytime is usually greater than that we provide for our eyes after dark, and it is after dark that many people have to carry out their domestic tasks, many of which are severe from the eyesight point of view.

Studies in psychology have proved beyond argument that conditions which are conducive to comfort and cheer- fulness have a great influence on our general health, and scientists and lighting experts the world over have proved tant part in our lives. that from this point of view light plays a most impor-

Given a free choice, the average person chooses between 50 and 200 foot-candles for ordinary reading, and although it is not yet possible to provide these levels of illumination in every home economically, it is hoped that a study of the series of articles given in this publica- tion will indicate the way to improve the existing standard of home lighting considerably.