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70 A. S. HowEUv AND J. A. DUBRAY [j. s. M. p. E.
Since we are at the present time in the field of generalities, it may be appropriate to survey the problems pertaining to the photographic and projection optical systems.
In Fig. 5 (1) are shown at B, C, and D, the areas of aberrationless covering power that a photographic objective must possess for the three proposed new dimensions, and, at A, for the 18 X 24 mm. image dimension, which is the standard in force for the 35 mm. film. Both camera and projector apertures have been traced.
Photographic Objective. — In Fig. 5 (2) the photographic objective is represented in its simplest expression, with the point N representing a system in which the two nodal points coincide.
If we consider a lens of 50 mm. focal length, focused at infinity as the standard, since such a lens is the most used in actual practice for an image size of 24 mm. width, we find that:
A 62.* mm. (2l/2") lens will embrace the same object space width for the image size of 30.76 mm. width of the "Economic" dimension.
A 77.2 mm. (3") lens will embrace the same object space width for the image size of 35.33 mm. width of the "Spectacular."
A 94.1 mm. (33//) lens will embrace the same object space width for the image size of 46.31 width of the "Extreme" dimension.
If we now take as a point of departure a 35 mm. lens as the shortest focal length lens used in actual studio practice, we find that in order to cover the same object space width we shall use, for the "Economic" dimension, a lens of a focal length of approximately 45 mm., one of approximately 55 mm. focal length for the "Spectacular," and one of approximately 67 mm. for the "Extreme."
This brings to our attention the fact that for the same distance from object to camera, and in order to photograph the same object space width, the wider area film would require the use of lenses of longer focal length than those in use today with the 35 mm. standard film.
This phase of the question is important in regard to the depth perspective of the sets photographed. There is no question in our minds that the use of lenses of extremely short focal length, such as 35 mm., introduces a noticeable and disturbing distortion in the perspective depth rendition of the average motion picture set. It is our belief that the use of, say, a 47 mm. lens, instead of a 35 mm., would tend to add to the beauty and naturalness of the picture.
It is well known that studio practice requires that all scenes pertaining to one single sequence of a talking picture be photo