1、 1 Scope This practice specifies the optimum installation parameters for gains screens used in motion-picture theaters. 2 Considerations 2.1 A gain screen is any screen surface with a gain of 1.1 or more. Gain determination of screens is specified in SMPTE RP 94. 2.2 The effect of the screen gain is
2、 reduced when the angle of viewing is increased away from the major reflected rays (see annex A.4). 2.3 When the light projection is perpendicular to the screen surface, the effect of gain diminishes in every direction away from the perpendicular condition to the screen center. 2.4 Specular screens
3、follow the physical law; i.e., the angle of incidence equals the angle of reflection. 3 Formulas 3.1 Radius of screen The screen shall be curved when installed to a radius of: 2center audience and screen betweenDistance distance Projection +3.2 Degree of tilt To have maximum gain aimed at the center
4、 of the audience, the screen shall be tilted as follows: 2center screen to angle ProjectionPage 1 of 2 pages RP 95-2003 Revision of RP 95-1994 Copyright 2003 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 595 W. Hartsdale Ave., White Plains, NY 10607 (914) 761-1100 Approved October 20, 20
5、03 SMPTE RECOMMENDED PRACTICE Installation of Gain Screens RP 95-2003 Page 2 of 2 pages Annex A (informative) Additional data A.1 With gain screens, it is best to locate the audience inside the one-half maximum gain angles; good audience coverage can be attained if the audience boundaries are define
6、d by the angles at which the gain is no less than that necessary to provide the recommended screen luminance (see SMPTE 196M). A.2 Retroflective or beaded-type screens shall be avoided unless the projector is in the center of the audience. A.3 Higher gain screens (1.5 and higher), and all silver scr
7、eens should be installed in curved form to avoid the objectionable hot-spot. A.4 Nearly all gain screens have a mirror effect, which causes the angle of projection reaching the sides of the screen to be reflected toward the walls unless the installation is in curved form. A.5 Where the audience seat
8、ing is wider than the screen width, consideration should be given to a ray-trace of reflected light from the gain screen, so that the light properly reaches the side seats across the middle rows. Ray-tracing can be done by hand drawing or by computer and may differ from the formulas given in 3.1 and
9、 3.2, especially with shorter focal length lenses, such as the range of 50-mm to 75-mm focal length for 35-mm anamorphic projection from a rear projection booth A.6 Use of a curved screen with vertical projection angles greater than 8 requires consideration of curvilinear distortion, and may require adjustment of screen masking. Annex B (informative) Bibliography SMPTE 196M-2003, Motion-Picture Film Indoor Theater and Review Room Projection Screen Luminance and Viewing Conditions SMPTE RP 94-2000, Gain Determination of Front Projection Screens .
