Overview
ISO 11315-2:1997 - "Photography - Projection in indoor rooms - Part 2: Screen luminance test for still and video projection" defines a standard method for measuring screen luminance in darkened indoor projection rooms. It treats the screen as an integral part of the projection system and establishes repeatable measurement procedures so different projectors and screens can be compared under practical viewing conditions. Electronic monitor-type displays and holographic systems are excluded.
Key topics and technical requirements
- Scope: Measurement of luminance for optical still and video projection in darkened rooms; screen considered part of the optical system.
- Measurement geometry: Luminance is measured at three test points on the screen (centre and two side points) from three viewing positions in the seating area (central position A and two transverse positions B and C).
- Viewing-area positions: Measuring device placed approximately 1 m above the floor at 2/3 of the distance from the screen to the last row; transverse positions are ±(1/2 screen width) from the centre.
- Measuring device: Luminance meter with field angle ≤ 1.5°, spectral sensitivity of a Standard Colorimetric Observer (CIE 15.2), measurement inaccuracy ≤ ±10%, and compliance with Class B per CIE No. 69.
- Uniformity ratio (g): Evenness is quantified as g = (Lmin / Lmax) × 100% - calculated from centre and side point measurements; minimum acceptable g = 50%.
- Recommended luminance: Centre luminance L2 ~ 50 cd/m² ± 15 cd/m² for public projection; lower limit of 35 cd/m² to preserve colour and detail.
- Spectral distribution: For incandescent (tungsten) sources approximate black-body at 3200 K ± 350 K; for Xenon sources around 5400 K ± 400 K.
- Frequency: Re-measure centre luminance at least every three months to track lamp ageing and system drift.
Applications and users
ISO 11315-2 is practical for:
- AV integrators and cinema/lecture-hall technicians verifying projector and screen performance
- Screen manufacturers and quality-control laboratories testing reflected/transmitted luminance
- Museums, universities, conference centres, and auditoriums ensuring consistent viewing conditions
- Projector rental companies and multi-projector installations performing luminance matching
Benefits include standardized comparisons across equipment, consistent image appearance for audiences, and guidance for multi-projector matching (luminance and colour temperature tolerances).
Related standards
- ISO 11315-1:1997 - Screen illumination test for still projectors
- ISO 11315-3 / 11315-4 - Projection screen properties and classification (distribution, indicatrix)
- ISO 2910:1990 - Screen luminance for motion-picture projection
- CIE No. 15.2 and CIE No. 69 - Colorimetry and luminance meter performance
Keywords: ISO 11315-2:1997, screen luminance, projection measurement, uniformity ratio, luminance meter, still and video projection.