SMPTE RP 12-1997 (Stabilized 2012)

This practice specifies the luminance (measured brightness) of the projection screens for drive-in theaters intended for the projection of motion-picture film at 24 frames/sec.
The practice defines luminance ratios among portions of the total screen area, and defines the acceptable variations as viewed from positions within the audience area.
The practice applies to both diffusing and directional screens.