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RAYTONE
HILUX
PRODUCTS
FOR GUARANTEED
RAYTONE Screens, Hilux Lenses, Thompson Screen Frames, Raytone Screen Paints and Screen Brushes will meet all of the manufacturer's claims.
RAYTONE SCREEN CORP.
165 Clermont Ave., Brooklyn 5, N. Y MIDWEST: L. E, Cooley,
408 Oak Park Ave., Oak Park, III.
GREATER
Durability in
GRIGGS
CHAIRS
Superior construction gives years of service.
Comfort — the minute they're occupied!
Their Beauty sparkles!
WRITE FOR CATALOG
GRIGGS EQUIPMENT CO.
Belton, Texas
SELECTIFIERS
SELECT-A-VOLTAGE
SELENIUM
RECTIFIERS
“50,000 HRS.”
OR
"Superior" MODELS
50 A. to 400 A.
ADJUSTABLE-IN-USE
Continuous
FIRST
LOWEST
USE
SEE: DOC FAIGE TESMA BOOTH 124
COST
NORPAT, Inc.
1 13 W. 42nd St.. N.Y.C
YOUR QUESTIONS ARE INVITED. If you have a problem of design or maintenance the editors of BETTER THEATRES will be glad to offer suggestions. Please be as specific as possible so that questions may be answered most helpfully. Address your letter to BETTER THEATRES SERVICE DEPARTMENT, Rockefeller Center, New York.
case of anamorphic VistaVision, the width of the screen that can be accommodated would be 78 feet wide. With optical print CinemaScope, the screen width could be 92 feet, and with four-track CinemaScope the screen width could be 100 feet. (All figures given for systems using anamorphic lenses have recognized the existence of a light loss of about 8% introduced by the anamorphic lens attachment.)
If the screen, instead of having a matte white surface, is an aluminized paint surface, with a reflection factor of approximately 1.4, the non-anamorphic Vista
is calculated to allow a 133-foot picture with center brightness of 4 foot-lamberts.
When the center brightness on a screen is 4 foot-lamberts, with a typical distribution pattern, the average brightness over the whole surface of the screen is found, by test, to be 2.9 foot-lamberts.
With a screen having a reflectance factor of 1.4, it is only necessary to project 2.05 foot-candles to the screen to realize the 2.9 foot-lambert brightness. The 31,000 lumens available today through a CinemaScope aperture, with standard f/2.0 optics, is reduced by the 50% shutter loss and the
Summary of Wide-Screen Projection Systems Applied To Drive-Ins
Compiled by ARTHUR J. HATCH, vice-president, Strong Electric Corporation
System
type
Aperture
size
Aperture area (sq. in.)
Lumens thru apert.
Type of Screen
Aspect
Ratio
Screen
Size*
Width
Factor
Standard
.825 x .600
.495
23,500
matte
1.33:1
66 x 50
1.00
VistaVis. reg. standard
.825 x .446
.368
17,500
matte
1.85:1
66x36
1.00
VistaVis.
squeeze
.825 x .600
.495
23,500
matte
2:1
78 x39
1.18
VistaVis.
standard
.825 x .446
.368
17,500
alum.
1.85:1
89x48
1.35
CinScope
optical
.839 x .7 1 5
.600
28,500
matte
2:35:1
92 x 39
1.40
CinScope
4-traclc
.912 x .715
.652
3 1 ,000
matte
2.55:1
100x39
1.52
VistaVis.
squeeze
.825 x .600
.495
23,500
alum.
2:1
102x51
1.55
CinScope
optical
.839 x .7 1 5
.600
28,500
alum.
2.35:1
122 x 52
1.85
CinScope
4-track
.9 1 2 x .7 1 5
.652
3 1 ,000
alum.
2.55:1
133 x 52
2:00
* Based on 4 foot-lamberts at center. tScreen width ratio factor explained in text.
Vision picture width could be 89 feet, anamorphic VistaVision 102 feet, the CinemaScope optical picture 122 feet, and the CinemaScope four-track picture 133 feet in width — which, incidentally, is about the maximum size that is being used in present day drive-ins.
The accompanying chart shows these various figures for the different types of projection systems and different types of screens. All the figures shown are based on the use of the most powerful projection arc lamps available to day; and the sizes of the screen are calculated so that a brightness of 4 foot-lamberts will be obtained in the center of a drive-in screen when the shutter is running. This figure of 4 foot-lamberts is a bit above the average brightness we find in most drive-in theatres today.
To explain how these screen widths have been arrived at, let us take, for example, the four-track CinemaScope system which
8% anamorphic lens loss, so that the incident light on the screen is 14,350 lumens. Since lumens are the product of average foot-candles times screen area, we obtain the area that we can illuminate to this 2.05 foot-candles intensity by dividing 14,350 by 2.05, for a resulting screen area of 7,000 square feet.
The picture width can be computed by taking the square root of the product of screen area times screen aspect ratio, which, in the example, calculates to 133 feet wide. The other calculations in the chart were made in a similar manner for the other projection systems and screens.
Assuming any particular theatre to have ample screen illumination on a matte screen using standard size aperture, the screen width that can be illuminated to the same brightness for any of the wide screen systems can be calculated by multiplying the present screen width by the width ratio fac( Continued on page 40)
36
MOTION PICTURE HERALD, OCTOBER 2, 1954