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HANDBOOK OF PROJECTION FOR
ground. Project it, and if there are white streaks up and down from the letters, or from white objects in the picture, move the shutter slightly by pulling it around. If this makes the matter worse, then you have moved it the wrong way. Move the shutter until the white streaks disappear, whereupon you are all right. That is all there is to "setting the shutter."
If there should be travel ghost both up and down it is evidence that the master blade of the shutter is not wide enough. A condition of this kind may be eliminated by riveting a small, light piece of sheet metal to each edge of the shutter blade (each edge to preserve the balance) or by
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Figure 229.
moving the shutter to a more narrow point of the light ray, if it is not already at the narrowest point.
ONE-AND-A-HALF-TO-ONE SHUTTER.— This type of shutter is in effect a three-wing shutter, though it has but two blades. This is by reason of the fact that instead of revolving once to each complete cycle of the intermittent, as do other shutters, it makes one-and-a-half revolutions to each cycle of the intermittent. This means that if we number its two blades 1 and 2, and No. 1 is master blade at the movement of the intermittent, No. 2 acts as flicker blade and No. 1 does also, No. 2 coming in front of the lens as master blade at the next movement of the intermittent. This type of shutter-^has the advantage of high speed, which causes the