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1953-54 Theatre Catalog, 11th Edition, Page 269 (233)

1953-54 Theatre Catalog, 11th Edition
1953-54 Theatre Catalog
1953-54 Theatre Catalog, 11th Edition, Page 269
Page 269

1953-54 Theatre Catalog, 11th Edition, Page 269


2. Interlock the projectors with shut ters and motors in absolute sync.

3. Center the framing control of both machines.

4. Thread up a loop in each machine in frame and in sync with the emulsion position as indicated in Note 1. Start the projectors in interlock, open the dowser in the right machine (as you face the screen) and center the chart on the screen by means of the framing control. If possible, reduce light while running the loops in order to minimize film warping, which in turn affects focus.

6. Center the chart in the other direction by shifting the projector.

7. Level this projector so that the wide horizontal line on the chart is parallel to the bottom masking of the screen.

8. This right projector should then be well locked off, as subsequent adjustments are made with the left projector.

9. Open the left dowser and superimose the two Xis at the center of the chart by adjusting the left projector with the framing control and by shifting the projector.

10. The vertical center lines should be superimposed. If they are not superimposed, level the left projector.

11. There may be some loss of matching in the corners of the screen due to keystone. This cannot be corrected.


Because of differences in photographic techniques, either the left print or the right print or both may be projected emulsion-toward-the-light or emulsiontoward-the-lens. In any case the sound track will be on the proper edge of the film. Therefore, to be certain of proper alignment the test loops should be threaded with the emulsion in the same position as it is on the prints to be projected.

Where a loop is reversed the target will be upside down. This is satisfactory as the loops can be used with both targets upright, with both upside down, or with one upright and one upside down, and give a proper alignment.

This procedure is advisable because if the optical axis of either lens is not correctly centered. reversing the emulsion position and refocusing will cause a horie zontal shift of the picture on the screen.

Do not consider this lineup as a final focus check. Always focus for 3eD projection through the filters and refocus without filters for regular pictures.

The alignment of the projectors should be checked frequently as vibration may cause the projectors to get out of alignment. Always realign for a 3-D feature which does not have the same emulsion


Additional Uses of the Target Alignment Loops

l. Crosshatching outside the chart area should not be visible on the screen.

2. The letter (A) will appear in each corner just inside the screen border when the picture is the proper size and is centered properly on the screen.



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ABOVE IS A POLAROID FILTER which must be placed over the proper port and installed so that light

passes through the center.

3. The small white squares will indicate travel ghost if present.

4. The black steps on the four sides of the picture indicate jump and weave, one per cent for each step.

5. The small lines in the big white cross provide an over-all check of the center-to-side focus.


Projection light requirements for 3-D present a very practical problem to the exhibitor and projectionist. Besides having to run both lamps all the time and to run them with equal light output, there needs to be substantially more light from each lamp than with 2-D. That is because the polarizing filter at the projector rejects almost half of the light falling on it and the viewing filter rejects about half of what is left.

3-D screens will heln. Because of their design more light will be directed toword the seats and less toward the side walls and ceiling. Even so, to compensate completely giving each eye a picture as bright as with 2-D using a release print of normal density, the light coming through the projection lens would need to be increased by two and a half times. That is a big order.

Producers and their laboratories are well aware of this and will likely go as far as is safe in adjusting print density or color balance or both to help relieve the situation. For practical results if the light output from each projection machine is doubled results should be quite satisfactory.

Picture brightness from both machines. If it is not, the stereo effect will be decreased as thn brightness difference becomes worse. No

should be equal

Filters must he vertical and as far as possible 1.0m projector lens.

one has named an exact figure as a tolerable limit but estimates range from 10 per cent to 20 per cent. Variations of that amounteone or two foot lamberts on a screen that averages around 10 foot lamberts of brightnesseare to be expected from minute to minute in normal good operation. These variations are caused by rotation of the carbons, fluctuations in current drawn at the gap, air drafts through the lamp house and consequent temperature changes. Since it just isnit practical to control everything all at once, we cant expect perfection. If lamps are clean and in line, if carbons are kept always in trim and if lenses and mirrors are cleaned reg ularly, brightness difference troubles arenit likely to be serious. SYNCHRONIZATION

The success of 3-D depends upon good projection and good projection demands exact synchronization between the two interlocked projectors. Not only must the proper pair of left and right eye images appear on the screen at the same time but also the shutters must be exactly synchronized.

If the two pictures are out of sync by one frame. the 3-D illusion will be seriously affected and may be destroyed entirely on scenes with fast action. The film laboratories and exchanges are going to great lengths to insure that paired prints are properly synchronized through out, damaged portions of one of the films will be replaced with black frameline loader and footage numbers will be checked to determine whether any film has been lost bv breaks in the theatre.

Shutter synchrnni":1ti0n can be made exact with either Selsyn interlock motor
1953-54 Theatre Catalog, 11th Edition, Page 269