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THE I.ICIIT SOURCE
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setting, or the appearance of light source is often misleading.
Ventilation for Mich [ntensity Lamps
(80) Heat in the lamphouse is injurious to its wires, insulation and other materials and is very trying to the projectionist. On the other hand too much ventilation makes the light source unstable. (81) It is a safe rule to have all the ventilation possible without disturbing the light source. The projector shutters now used direct a strong blast of air toward the lamphouse and it is well to protect the forward vent holes with a metal shield having an opening at the sides.
(82) Always have the dowser closed when you strike a high intensity arc, but do not keep the dowser down too long while arc is burning unless you want a damaged dowser blade. If the dowser is not down while you strike arc you may get a badly pitted collector lens. The high intensity arc throws off minute particles of incandescent carbon at the instant of striking the arc.
(83) After each reel is run, examine the collector lens or mirror and brush off any ash or dust that may adhere to its surface.
Reflector Type High Intensity Light Source
(84) All that has been said of the straight H. I. light source applies equally to the reflector type H. I. light source. The equipment involved is different in many ways, but the light source is exactly the same, only its amperage limit being lower, (85) its range being from 60 to 85 amperes. In some makes of lamp the negative is carried at essentially the same angle as in straight high intensity light sources. In others the angle is much less.
Low Intensity Reflector Type Light Source
(86) When properly handled this type supplies an amazing amount of very white light per watt of power consumed. (87) First, the light source area is small and therefore well adapted to an aperture of limited dimen