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Condenser System for Wide Film
by
EUGENE H. ROONEY
(Reprinted from Projection Engineering, this being in our opinion vital information to every projectionist.— Editor).
The recent success of wide film and its probable adoption by the motion picture industry now brings to light a most perplexing problem. Considering the new standards of screen size and the change in film aperture to 1 :2, it is more difficult to obtain a brilliant and uniform screen illumination free from chromatic aberration and ghosts.
Until last year the condenser system available consisted of a pair of piano convex lenses of different diameters and focal lengths. The most light thereby obtained on the screen with the use of one of the best high intensity arc lamps amounted to about 5,500 lumens.
It is a known fact that a parallel beam of light overcomes distance more efficiently. This thought caused the use of parabolic condensers. Since the film window is rectangular, the projection of a round spot means a waste of light. A full spot covering all four corners of the rectangular window was finally developed by means of grinding a horizontal curve on one side of a condenser, thereby broadening the beam of light in one direction. Steps were also taken to increase the amount of light emanating from the arc, in other words, the collecting angle was enlarged.
After the above tests and extensive research work in conjunction with both foreign and domestic optical firms, the Fish-Schurman Cor
poration of New York finally presented a special condenser system for wide film projection. This system consists of :
one 5 Yz diameter Grand Special A cylindrical, spherical, bi-convex and
one 6" diameter Grand Special B parabolic, convex-concave.
It is made of genuine optical glass and the amount of light is increased to about 10,000 lumens to 15,000 lumens compared with the 5,500 lumens for the old system.
Considering the extreme heat to which a condenser is subjected, it is essential that it be made of special heat-resisting glass like IGNAL, which defies the heat and represents the best type of genuine optical glass.
The arrangement of the S. O. G. Condenser System, as seen in the illustration, is carried through as follows : Grand Special A is placed
with its cylindrical curve about 3 y2" from the arc, its two marked lines in a horizontal position. Grand Special B is placed with its concave side as close as possible to the spherical convex side of Grand Special A, without, however, touching it.
RITUAL EQUIPMENT BUILT
A problem to many chapters has been solved by Bro. C. D. Fink, 572 Burdick Drive, Pomona, Calif. He has built a handsome set of pedestals for use in initiation. They are of modernistic design and are well made in every respect. They would be a splendid addition to any chapter’s equipment. Any chapter desiring these pedestals should communicate with Bro. Fink direct.
T hirty -fiv e