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1954-55 Theatre Catalog, 12th Edition, Page 314 (278)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 314
Page 314

1954-55 Theatre Catalog, 12th Edition, Page 314

Those who project the films are at the end of a long chain in which everyone must do his part well or success changes to failure.


Figure 4 illustrates, in another way, the changes in screen density and picture quality for five different regions of print density as the amount of stray light relative to the screen brightness is varied. For the average drive-in theatre, good picture quality is seldom possible on a clear evening until approximately 50 minutes after sunset. (Here a 3 ft-L screen brightness is assumed for a projection screen facing away from the sunset.) Since some itdrive-ins" start picture projection at 9:00 p.m. E.D.T. during June and July in the Rochester area, and the remainder are in operation before 9:15 p.m., the stray-light level on the screen at the start of the show is actually equal to the brightness from the projector.

Therefore, it has become customary practice at these "drive-ins" to begin their show with a cartoon. Since cartoons are usually composed of light

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FIGURE 3 shows tone reproduction ot a reversal color print with a constant stray-light brightness of 0.10 tt-I. on the projection screen. Audience reaction for various levels is indicated on lett.

density scenes, they are naturally least affected by the stray light present on the screen.

During the period of full moon, the stray-light brightness of the outdoor screen may climb to more than one per cent for the average ttdrive-in" possessing a screen brightness of 3.0 ft-L and probably will exceed three per cent for those operating at screen brightnesses in region of 1.0 ft-L. Under these condi tions, the viewer may experience great difficulty in following any of the action in the dark scenes.

Fluctuations in the stray-light level can also become a problem in other situations, for example, the classroom, even though the quality of the light which is being projected may be rated as excellent. The compression in the screen density range, as a result of stray light, is most noticeable in the dark shadow regions of the print, since, in this situation, density is lost much faster than in the light areas. After studying Figure 4, it is .not difficult to see why the dark shadow areas of the picture lose their identity when stray light becomes excessive.

In making the screen-brightness survey at these six drive-in theatres, data were also recorded on the projection equipment, including projection lenses, type of carbon, .arc current, and lightcollecting mirror or lens. Measurements were made to determine the percent reflectance of the screen as well as the total light output of the projectors.

On the basis of this information, the following results were calculated:

1954-55 Theatre Catalog, 12th Edition, Page 314