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1954-55 Theatre Catalog, 12th Edition, Page 261 (225)

1954-55 Theatre Catalog, 12th Edition
1954-55 Theatre Catalog
1954-55 Theatre Catalog, 12th Edition, Page 261
Page 261

1954-55 Theatre Catalog, 12th Edition, Page 261

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in the port to restrain the booth noises from the auditorium, a good grade of optical glass, preferably with antireflection coatings, should be installed. Too frequently poor glass has been used and loss of definition charged to other sources. With the greater magnifications being used in the various processes this factor is more important than ever.


The screens recommended for use with CinemaScope are of the controlled reflectance type, with metallic surfaces, which are the result of many years' development.

Miracle Mirror screens are made with a cotton base which is overlaid with several coatings of plastic surfaced with aluminum and accurately embossed with a fine detail pattern. The pattern is designed so that very little light is reflected to the average theatre auditorium where there are not seats but within the theatre seating regions the distribution is quite uniform. The uniform area of distribution includes 30 degrees above and below and 50 degrees to each side of a line perpendicular to the screen. It will be recognized that the typical theatre is adequately covered. By concentrating all of the incident light only to the regions of the audience, a screen is obtained which is at least twice as bright as the usual theatre screen for the same value of projector illumination. By virtue of the metallic surface the screen supplied for CinemaScope is excellent for 3-D polarized projection. The screen material is purposely made light in weight to facilitate hanging and to minimize the demands on screen


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FIGURE 6 also provides data about the setting and unfolded scale for the lens attachment.

frames and, became of this, it cannot be handled roughly; it is adequately strong if treated with reasonable care. The finer detailed surface can be damaged by severe rubbing or pressing and will be evidenced by dark spots which cannot be removed. No attempt should be made to clean or resurface the screen but it may be dusted with a soft dusting brush. The surface is such that it does not collect dust readily and does not discolor or oxidize easily. Experience has shown that the useful life of these screens is several times that of the ordinary white screen.

The screens should conform to the appropriate Federal specification applicable to the testing of such materials for fire resistance and flame proofing and although they will char and smolder when subjected to flame, combustion will not be supported.


The Miracle Mirror screen is available in two patterns: one for head-on projection and a tilted design for high-angled projection. The result from the two patterns of the Miracle Mirror for 20 degrees projection is shown in Figure 7. It is obvious that the head-on pattern with high-angle projection would not reflect much light to a high balcony area, whereas the tilted design would serve admirably. The choice of pattern depends on the specific theatre conditions. A further choice resides in the possibility of tilting the top of the screen away from the projector a few degrees, up to



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five degrees or six degrees. In high angle projection this serves two purposes, first and primarily, to minimize picture keystone effect and, of secondary importance, to give more control of the vertical light distribution. A typical situation is shown in Figure 8.

A curved screen whose radius is approximately that of the projection throw has several real engineering advantages. When dealing with very wide pictures the angle at which the light beam strikes a fiat screen at the sides is far from head-on and with restricted angles of reflection some of the side seats would not have adequate picture brightness; this is corrected with suitable curvature. Secondly, there is less overall picture distortion for side as well as for headon viewing. Thirdly, picture definition at the sides may, under some circumstances, be improved. Curved screens do introduce one difficulty and that is the curvature of horizontal lines. of the image. This difficulty can be reduced by the use of a slight tilt as described above. 'For short throws and steepip'rojection angles, which produce severe curvature i of horizontal lines, it ' may, be better to I} compromise "the curvature slightly and install a Screen which is somewhat flatter than dictated by the projection distance. It. should-"be recog: nized that when a curved screen is tilted the ends rise and due consideration must be given to sight lines, frameaconstruction and masking. , '

Picture size, on a fiat screen with head-on projection, for various projection throws and lcnsos with the CinemaScope aperture are shown in Table I. When a curved screen is used whose
1954-55 Theatre Catalog, 12th Edition, Page 261