Brightness uniformity
How evenly light falls across the image: the corner (or edge) illuminance as a share of the centre.
- Unit
- %
- Standard
- ISO/IEC 21118 (centre-to-corner ratio, production average)
- ISO 21118
- ISO 21118 optional
- Better
- ↑ Higher
- Status
- Standard reference being re-verified
- Mean illuminance
- 313 lux
- Image area
- 2.25 m²
- Light output
- 705 lm
- mean lux × m²
- Uniformity
- 62 %
- darkest Ă· brightest
Show the numbers
| Point 1 | 260 lux |
|---|---|
| Point 2 | 340 lux |
| Point 3 | 260 lux |
| Point 4 | 340 lux |
| Point 5 | 420 lux |
| Point 6 | 340 lux |
| Point 7 | 260 lux |
| Point 8 | 340 lux |
| Point 9 | 260 lux |
| Lumens | 705.0 lm |
| Uniformity | 61.9 % |
The 9-point method (IEC 61947-1, the basis of ISO/IEC 21118 light output and the old ANSI lumens): measure illuminance at nine points of a 3Ă—3 grid, average them, multiply by the image area. Uniformity here is the darkest point as a percentage of the brightest. ISO 21118 states production averages, and shipped units must reach at least 80% of the stated value.
How to compare it
Brightness uniformity (centre-to-corner)(%)
≥85% is good, below 75% shows visible vignetting. UST and short-throw are typically worse.
Marketing traps
- Brightness uniformity (centre-to-corner): The formula varies: min corner Ă· centre, or average of corners Ă· centre. Read the method. ISO's exact formula needs a check against the full text.
Across the catalogue
Deep cut
Brightness uniformity (centre-to-corner). Uniformity drops further with lens shift towards its extremes and with high-gain screens (hot-spotting). Colour uniformity (tinted corners) is a separate problem, measured as Δu′v′ across the field.
Terms on this page
Brightness uniformity
The ratio of the darkest to the brightest of the 9 (or 13) measurement points, as a %. ⚖ brightness.uniformity_pct ↑