The anamorphic lenses supplied with the CinemaScope Package have been designed as frontal attachments to the regular projection lenses, and represent an approximate 6 1/2" of extension beyond such projection lenses in installations using projection lenses of a diameter of 2-25/32", and an approximate 9 1/2" in installations using projection lenses of a diameter of 4".

At the present time, projection lenses of focal lengths of 5.00" or less are furnished in barrel diameters of 2-25/32", and projection lenses in focal lengths of 5.25" and over are furnished in barrel diameters of 4.00", though in older types these longer focal length lenses appear in the smaller diameter barrels. It is recommended, however, that this latter type be replaced by new, higher quality, high-speed lenses.

Should the surveyed projection heads be fitted with a shutter in front of the projection lens, some modification of that arrangement may be necessary.

Some present projection lenses may not be of sufficiently high quality to permit the undistorted projection of the CinemaScope picture and replacement of such projection lenses is desirable, and may be essential.

Should the survey indicate a change in picture height outside of the range set forth in THE APERTURE, then additional projection lenses are required in any event, and these in all cases should be of high quality and should have a flat field.

The aperture and the anamorphic lens have been designed to produce a picture of an aspect ratio of 2.55 to 1; that is, the width is 2.55 times the height.

The aperture dimension for the CinemaScope picture is .715" x .912", resulting in an increase in height of the present picture by about one-sixth if the present projection lenses are retained. In practice, this dimension is entirely actual only in the case of head-on projection.

In angular projection, that is at greater angles of projection throw than zero degrees, the aperture plate, being, delivered with a lesser opening than its nominal dimension, may be filed to the opening required by the individual situation as a correction for keystoning.

This, as at present, is an on-the-job operation.

Accompanying these instructions are two charts being (a) a chart of the CinemaScope picture sizes resulting from the use of various focal length lenses at various throws at intervals of 10', and (b) a similar chart of picture sizes for the present conventional aperture of .600" x .825", obtained from the use of various focal length lenses at various throws, also in the intervals of 10'.

An examination of the chart indicates that for the same picture height, different size projection lenses will be required for the CinemaScope picture and for the present conventional picture.

Since heights increase somewhat with the angle of the throw, some account must be taken of this difference.

The actual picture widths given in the CinemaScope tables are figured upon the chord of the screen and not upon the arc.

For definitions of the terms chord, arc, rise and radius as they apply to the CinemaScope picture, see the chart and diagrams covering these terms and fixing these dimensions.

Since the beam from the anamorphic lens diverges immediately it leaves the lens, and the width of the beam is, generally speaking, more than double the width of the present beam, the present beam should be measured at the port and at any enframement of the port to determine the width required for the CinemaScope beam, and where necessary, ports must be enlarged and enframement of the ports cut away.