Obtrusive light checker

How this is calculated#

The tool estimates the light a floodlight or bollard puts on a neighbour window. It checks the result against AS/NZS 4282:2023.

1. Zone and period. You pick the environmental zone, A0 to A4, and whether the curfew applies. Table 3.1 defines the zones. Cl 3.2.4 sets the curfew period.
2. Intensity toward the window. The tool takes the beam angle and the tilt of each luminaire. It finds the angle off the beam axis. It then reads the intensity at that angle from a simple lobe (Cl 3.3.1.3).
3. Vertical illuminance. For each luminaire, it divides the intensity by the squared distance to the window. It applies the maintenance factor of Cl 3.2.2 and adds the luminaires.
4. Illuminance limit. Table 3.2 gives the vertical illuminance limit for the zone and period.
5. Intensity limit. Table 3.3 gives the intensity limit for one luminaire. The tool uses the Level 1 value.
6. Upward light ratio. Cl 3.3.1.8.2 gives the share of lumens above the horizontal. Table 3.2 gives the limit.

Worked example#

• Two floodlights at a window 10 m away. Each unit gives 10,000 lm, mounted at 6 m and tilted 30°. Zone A2 applies outside the curfew. The tool gives 47.67 lx at the window against a limit of 5 lx, so it fails. The intensity of 3,143 cd is under the limit of 7,500 cd. The upward light ratio is 0.020 against 0.01, so that check also fails.

Limits#

The result is a point-source estimate. A site measurement rules. The tool uses a lobe in place of the photometric file from the maker. Use the maker intensity table when you have it. Only direct light counts. Reflected light and obstructions are not modelled.

Level 1 intensity applies. Level 2 needs a precedent from existing lighting (Cl 3.2.5). Tilting a luminaire can raise the upward fraction, so type the value at the aiming angle.

See also: Obtrusive light and the 4282 zones, Car park floodlight obtrusive light at a boundary and the lighting lumen tool.