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1954-55 Theatre Catalog, 12th Edition, Page 315 (279)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 315
Page 315

1954-55 Theatre Catalog, 12th Edition, Page 315


(a) Projector output as percent of theoretically available light

(b) Percent reflectance of screen

(c) Over-all eliiciency of the projection equipment including the


Average Range 56% 39% to 77% 72% 55% to 91% 40% 21% to 70%

With proper adjustment and maintenance, it is p0ssible to get these projectors to deliver to the screen at least 80 per cent of their rated available light output.s It is also possible to have the projection screens painted so that they Will reflect at least 80 per cent of the projected light.

The Results

Recalculating the results of the survey on this basis would give an average brightness for these six drive-in theatre screens of about 3.8 ft-L, a value approximately double that measured. Certainly this change would result in improved picture quality. Improvement would be especially noticeable in the case of one theatre where a few rapid adjustments prior to the survey more than doubled the screen brightness and where survey data indicated that this brightness could be increased again by another factor of three merely by replacing scratched mirrors and projection lenses, repainting the screen, and completely aligning the projector optical system. Adequate brightness is important, not only to overcome unavoidable stray light, but also to present pictures that are aristically pleasing.

After making any adjustments to the projector optical system, full attention must be paid to adequate cooling of the film at the projector gate. With the increase in screen illumination, there may be enough increase in the temperature of the film at the aperture to severely damage the print through blistering. Therefore, after the projector optical system is adjusted, it is wise to run a test film such as is described in the booklet, tiCOmmon Causes of Damage to 35mm Release Prints," which may be obtained from the Motion Picture Film Department, Eastman Kodak Company, Rochester 4, New York} (See 1952 THEATRE CATALOG, page 254.)

Motion picture film producers release their pictures so as to appear most satisfactory at the American Standard Screen Brightness for 35mm Motion Pictures of 9 to 14 ft-L. Many scientific tests covering the past 30 years or more of investigation have shown that the quality of pictures made to be shown at this brightness level is superior to the quality of the same films when projected at lower levels of screen brightness. Furthermore, the data indicate that it is better to make prints which are optimum for a screen brightness of approximately 10 ft-L even if they must sometimes be shown at 2 ft-L, than to make prints which are best for 2 ft-L knowing that usually they will be shown at the standard brightness of 10 ft-L.'


A. B.


Many farsighted managers of drivein theatres have invested a considerable amount of money installing highintensity projectors in order to obtain a better screen quality. However, purchasing and installing this equipment is not enough unless the equipment is carefully adjusted and maintained. Projection equipment poorly adjusted can easily be compared to a car whose motor is "out of tune? The poor adjustment robs the car of its performance


The following data have been collected from a screen-brightness and straylight survey of regular and drive-in theatres in the Rochester, New York, area. 1. REGULAR THEATRES-3 large (over 2200 seats)

5 small (300 to 1200 seats)

Screen brightness at the center of the screen.

Minimum brightness of the screen resulting from the normal operating light on the auditorium with projector turned tiOFF." Stray-light level on the screen during the projection of a normal density print.

Distance from booth to screen (Throw).

Average Range 11 ft-L 6 to 17 ft-L 0.006 ft-L 0.002 to 0.007 ft-L 0.03 ft-L 0.02 to 0.05 ft-L* or 0.3% of the screen brightness 140 feet 65 to 195 feet

'Tha highest stray-light condition was Iound in a theatre which used a light-colored drape directly behind the perforated projection ncreen.

2. DRIVE-IN THEATRES-6 with a capacity of 550 to 1000 cars


B. C.



STheso G.

Screen brightness at the center of the screen.

Width of screen.

Distance from booth to screen (Throw).

Brightness of the screen on dark nights with the projector turned ((OFFI,,

Total stray-light brightness on the screen relative to the screen brightness during the projection of a normal density print on a dark night. (This does not represent average conditions which would take into account early evening skylight, moonlight, or light scattered from the projector beam by rain, fog, or excessive dust in the atmosphere.)

Average Range 2.4 ft-L 1.3 to 3.2 ft-L . 52 feet 47 to 59 feet 240 feet 210 to 290 feet .003 ft-L .002 to .006 ft-L 0.6% 0.4% to 1.0%

The following data were collected at one drive-in theatre where the matte-painted screen faces east directly away from the setting sun. The data are reported for a clear evening in the month of March at 432 north latitude. (During June-July multiply the time in minutes after sunset by 1.3 as a result of the longer twilight period at thisttime of year.)

Minutes Stray Light on the Screen Relative After Sunset to a Screen Brightness of 2.2 ft-L

12 134% -2.95 ft-L Stray Light* 18 41% - 0.09 " i' ii 24 12% -0.27 " 'i j' 30 4.0% - 0.087 " it " 40 0.7% - 0.016 " " " 50 0.2% - 0.005 'i R "

:lrayvlighl values will be considerably higher for outdoor projection screen: which [ace the sunset. The brightness of the screen due to moonlight may reach approximately 0.02 ft-L or 1% of the screen brightness for the average drive-in. When the stray light produced by lens flare and scattered light from the projected light beam are added to that from moonlight, the total amount of stray-light is about 2% of the screen brightness. Even higher straylight ratios occur when there are other large sources of additional stray-light flooding the screen, where projection optical equipment is not in good condition, and where the screen brightness is lower than 2 ft-L.
1954-55 Theatre Catalog, 12th Edition, Page 315