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1954-55 Theatre Catalog, 12th Edition, Page 260 (224)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 260
Page 260

1954-55 Theatre Catalog, 12th Edition, Page 260

tachment is now ready for assembly with the-regular projection lens and installation of both into the projector. A final test of the adjustment is described later. It must be clearly understood that once the attachment has been properly adjusted it needs no further attention in this regard unless it is moved to some other equipment or changes in projection throw are made.

The setting for the projection throw is not a focusing adjustment; it merely adjusts the astigmatism of the attachment so that uniform definition is obtained over the whole screen area. The combination of the projector lens and CinemaScope attachment should next be rotated so that vertical lines in the center of the screen appear vertical and focusing of the projector lens is then accomplished in the usual manner by use of the customary knob and screw.

Under no circumstances should the attachment adjustment be changed as the projection lens and attachment are focused, except as described in the following:

The accuracy of the setting of the CinemaScope attachment can be checked at the time of installation by turning the focusing knob on the projector so that the images go out of focus slightly in each direction and observing that the horizontal and vertical lines of the image go out of focus simultaneously and at the same rate. For example, if turning the focusing knob clockwise

should make the horizontal lines fuzzyi

but the verticals should get a little sharper before becoming fuzzy, then adjustment of the CinemaScope attachment is indicated. Unlock the red clamp /////////////. ZWI,W%

y. W "J

n O O '0 V

ing ring and turn the uncolored knurled ring slightly in one direction and repeat the in-and-outmof zfocus test to see whether the change in horizontal and vertical lines occur together. If not, turn in the other direction slightly beyond the initial setting and recheck. When the best adjustment is found by this trial method lock the setting with the red clamping ring.

It is very important that great care be used in this test and, in evaluating the screen result, it should be remembered that the scales on the barrel were placed thereon in manufacture of the unit and suitably tested. If, after making this test carefully, and rechecking to make sure the observations are correct, the setting is different from the projection distance marked on the scale by more than five per cent, then the attachment should be returned for inspection.

Short focal length lenses require adaptor rings between the front of the lens and the CinemaScope attachment to assure that the latter will clear the head castings. These will be obtainable for the CinemaScope lens from the equip ment suppliers. Also, since the short lenSes are fitted quite deeply within the projectors there may be vignetting, or interference, at various places in the light path. The obstructions must be removed, either by filing or with redesigned parts.

The CinemaScope attachment is a high quality optical device and the glass surfaces have been treated to reduce reiiec FIGURE 5 offers information important when a CinemaScope lens attachment is being installed.

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tions at the glass-air boundaries. This tends to minimize flare, improve contrast and reduce light loss. When required, it should be cleaned with lens tissue and an appropriate lens cleaning fluid, the same as any other high quality optical element.

Projection Ports

Obviously, since the picture is approximately twice as wide for a given height as the past standards, it will usually be found that the projection port must be

widened out by an amount equivalent

to the width of the existing projection

beam measured at the auditorium side

of the port. A means to roughly calculate this is as follows:

(a) Multiply the distance of the face of the projection lens from the outer face of the wall of the projection booth (in inches) by 2.00;

(b) Divide the above result by the focal length of the projection lens (in inches);

(c) To this result add 4 inches

For example:

If the distance is 25 inches and the focal length is 5 inches ThenKA) = 25 x 2.00 = 50.00 inches (B) = 50.00 -j- 5 = 10.00 inches (C) = 10.00 + 4 = 14.00 inches or the minimum width of the port opens ing. In case the light beam passes through the wall of the booth at an angle thereto, the computed width must be increased to compensate for the angle and the thickness of the wall. For completeness, it should be noted that the port top or bottom, or both, might require change if the screen image height has been increased. When glass is used





1954-55 Theatre Catalog, 12th Edition, Page 260