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MANAGERS AND PROJECTIONISTS 656
TWO^WING AND THREE-WING SHUTTERS.— Except
in the case of 60 cycle A. C. we advise the use of the threewing shutter, provided the condition is such "that it can he at least fairly well optically balanced. It is true that as a general proposition the two-wing shutter will cut a somewhat less percentage of the light than the three-wing shutter, but it is also true that with modern brilliant projectionit is seldom possible to run a picture at normal speed when using a two-wing shutter, without producing flicker.
It does not necessarily follow that under all conditions the three-winger will produce appreciably less flicker at the given speed than the two-winger. We would suggest to tne projectionist that he test the matter by installing a threewing shutter and getting it into the best condition the local condition will allow. Project white light to the screen and .find out how low a speed it can be run at before flicker appears. Then put on a two-wing shutter and make the same test. If the two-wing shutter produces no flicker at the lowest speed you use, then the two-winger is to be preferred, but if it does produce flicker at your lowest speed, then the three-winger is to be preferred, because you can get all the really necessary screen brilliancy with it, and current is cheaper than flicker. Also it is better to have photoplays run at the proper speed, even though it be at the expense of some screen brilliancy.
We have explained all this at considerable length in order to give projectionists a clear understanding of the various points involved.
SETTING THE SHUTTER.— The setting of the revolving shutter is to the novice a very mysterious operation. It is, however, almost childishly simple once the underlying principle is understood. The master blade of the revolving shutter is, or should be, stamped with some distinguishing mark. If it is not, then you are safe in selecting the widest blade as the master blade. Loosen the shutter so that it may be revolved by pulling a little while you hold the projector fly-wheel stationary. Turn the fly-wheel until the intermittent sprocket is just barely ready to move, pull the shutter around in the direction it normally runs until its edge covers about three-quarters of the lens, tighten tne holding screws, but not so much that you cannot pull the shutter around on its hub or shaft by exerting a moderate amount of force. Thread a film into the projector, preferably one* having a white lettered title with black back