HEADLAMP LIMITATIONS

Evening Post, Volume CXXV, Issue 36, 12 February 1938, Page 28

HEADLAMP LIMITATIONS

Although little publicity is centred on improvement in the efficiency of headlights, worth-while'progress is being made. The headlamp industry is far from static. Large sums are expended aunually in the march - towards more effective lamps.

According to the manager of the U.S.A. Society of Automotive Engineers, there is' no necessary connection between bulb candle-power and glare. Owing to the concentrating effect of the reflector, he says, the lamp engineer can take a 32 candlepower bulb and produce candle-powers in the beam projected by the lamp of 10,000, 25,000, or more. Similarly, with a 50 candle-power bulb, he can produce candle-powers in the beam of 10,000, 25,000, or more. What candlepower in the beam amounts to, therefore, is largely a matter of design. Since the candle-powers in the beam are the important factor from the glare standpoint, it is obvious that placing a legal limit on bulb candlepower has little or nothing to do with the control of glare.

What limitation of bulb candlepower does is to set a maximum on the amount of light the engineer has to work with. If he wants to put more light in the high intensity portion of the beam, to make hazards down the road visible further ahead, he can only do so by reducing the amount of light in those portions of the beam which give foreground and lateral illumination. Similarly, if he wants better foreground or lateral illumination. h« has to take the light out of the high intensity portion of the beam.

At present the legal limit in many of the U.S.A. States and in other parts of the world is 32 candle-power. The limitations on bulb candle-power are being recognised as unfortunate by forward-looking highway administrators, and there are indications that, in some States at least, the limit will be raised or eliminated.'