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Monograph Model "AA" Double Shutter Projectors are designed and built to operate longer without costly repairs and replacements and consequently have the lowest possible ultimate cost. They assure maximum screen illumination without flicker. Smooth, quiet, cool operation. Buy Monograph; buy proven satisfaction.
Order from your Motiograph dealer or write
MONOGRAPH, INC. 4431 W. Lake St., Chicago 24, III.
Export Division (Except Canada)
Frazar & Hansen, Ltd., 301 Clay St.
San Francisco 11, California
Air Cooling Motion Picture Film for Higher Illumination
(Continued from page 18)
cle by Carver, Talbot, and Loomis1 a method of observing film position was described depending upon a gauge indicating the motion of the projection lens with respect to a fixed point on the projector mechanism.
This system has been preserved essen
hairs in the position that the image would occupy in film held perfectly flat in the gate.
Illumination is provided by a small headlight lamp, located in crater position so that the optical system of the lamp and projector is completely filled. When
FIG. 4. Mechanical film displacement as a function of air flow from nozzles. The 2 nozzles used in this experiment made an angle of about 30 degrees to the film plane, and in this position each tended to displace film in the direction of the air flow. The curves show the behavior of
freshly processed film without a previous projection history. Note that a resultant force capable of forcing film through zero, and even forcing it far positive, can be obtained if the emulsion side nozzle sufficiently overpowers the base side nozzle. Conversely, an overpowering base-side nozzle will hold firm in the desirable negative deflection.
+ 0.060
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+ 0.020
0.000
-0.020
-0.040
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600
1000
VELOCITY EMULSION SIDE -FT/SEC.
Velocity from
Base-Side
jrve
Nozzle, f.p.s.
1
0
2
250
3
360
4
520
5
745
6
1040
tially unchanged, with the substitution only of a dial gauge for the lever gauge originally used. This dial gauge indicates motion of the lens with respect to the projector frame.
Calibration to relate these values to actual film displacement from a flat plane in the gate makes use of a ground-steel gauge block with a small hole in its center, which holds thin glass-fiber cross
1 E. K. Carver, R. H. Talbot, and H. A. Loomis, "Effect of High-Intensity Arcs Upon 35-mm Film Projection," J. Soc. Mot. Pict. Eng., vol. 41, pp. 69-87; July, 1943.
the cross hairs are focused sharply on the screen, the gauge is set to zero.
The convention used in designating direction of film motion from this zero, it will be remembered, is to call motion toward the light source negative and motion toward the projection lens positive.
Maximum Drift Values
In the article it was pointed out that when the best visual focus is obtained upon the screen, the projection lens is actually focused upon the limit of film travel in the negative drift that is occur
UNBREAKABLE _
Non-Pitting /Uzstf3,
U GUARANTEED. 5 YEARS
Manuroclwrvd by
HEYER-SHULTZ, INC.
CEDAR GROVE, M. J,
Ofrtribufcd Exclusively by ' '■
MATIOMAL
26
INTERNATIONAL PROJECTIONIST • February 1950