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The Tungsten Arc
Still holding first place among the many inventions of recent years is the compact-source lamp marketed by B.T.H. Known as the Mazda Type-ME, it has an arc of tungsten in mercury vapour and a bulb of quartz instead of glass.
Those now widely used are of only 250 watts, but the light produced by them is far in excess of that produced by 1,000-watt filament lamps. The life of the new lamp is also greater than any filament lamp — 500 hours, as compared to only 30 hours for the latter.
For those who wish to incorporate the lamp in their own machines with the minimum of work, it is supplied already mounted within a special cylindrical cover and with a standard pre-focus base, which in most cases will allow it to be inserted in the lamphouse without too much trouble. Your reflector will not be needed and can be removed if it is in the way. But however you carry out the adaptation, the following precautions must be taken:
1. Stray light from the lamp must not be allowed to shine outside the projector. This is because the lamp produces a certain amount of ultra-violet light, which in time could make things rather unpleasant for the operator. To guard against such an eventuality, the lamp should be kept within its special casing. But there is no danger from the light transmitted by the lens.
2. The lamp should not be removed until it has cooled down and thus reduced its internal pressure. This is to guard against the (rare) possibility of it exploding.
Besides the above precautions, an adaption will also include some method of preventing flicker. The lamp strikes 100 times per second when working on A.C. 50-cycle mains and thus produces a slight but noticeable flicker, but as we mentioned in a previous chapter, this is easily overcome by running the projector at 25 frames per second, or by making a slight alteration to the setting of the shutter. But in spite of any such disadvantages, no-one can ignore the very real benefits possible by its adoption. It has a longer life and is therefore cheaper to use, and no other lamp yet made available to small-gauge users can produce such brilliance.
An even more powerful lamp, however, is now produced by the same company — a lamp which will give better colour
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