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MANAGERS AND PROJECTIONISTS 165
sidered that both reflection and ordinary absorption losses are recorded together with the color loss, it is seen that the color loss must be slight.
It does not, however, at all follow that color in condenser lenses is not harmful. As a matter of fact it is harmful, because it changes and injures the color value of the light. True, the color may not actually absorb very much of the total light, but it does alter and lower its value for projection purposes. For instance: The light from a condenser having a greenish cast is "muddy." It is not clear and brilliant, hence its value for projection purposes is lowered.
It seems, however, that the pink color sometimes found in condenser lenses which have been used for a time may possibly not be detrimental, but in fact beneficial. Now that we know color in the lens does not, as formerly presumed, necessarily mean excessive loss of light, it might be well to experiment with color to some extent, but if this is done the colors must be confined strictly to those tending to mellow the light, without seriously affecting its brilliancy. A slight pink tinge might be beneficial. At least this discovery opens up a field for investigation, though the fact that tinted film must be projected cannot be overlooked.
AVOID COLOR. — But in any event, except for experimental purposes, until this matter be finally settled, the projectionist should avoid all color. In purchasing lenses, any lens which shows the slightest trace of color, when looked through EDGEWISE, should be promptly rejected.
In examining lenses for discoloration, however, be very certain that any apparent color is actually in the lens itself, and not due to surroundings.
THROW THEM AWAY.— The projectionist should always look through his condenser lenses edgewise when cleaning them, and should any discoloration appear he should promptly discard the lens, explaining to the manager that the lens may in a very short time use up the price of a new lens in light brilliancy. This should invariably apply to green, and should be the rule for all colors, until such time as it may become an established fact that certain colors are desirable — if it ever is.
PITTED LENSES.— When using certain types of carbon there is a decided tendency to pitting of the collector lens. The question is often asked, does this pitting cause light loss? The answer is, to a certain extent, yes, but this loss is not as large as might be supposed. The pit consists of a spot