Spill light is light that reaches areas outside the intended outdoor target.
Spill light is light reaching outside the intended target surface. It should be recorded with aiming direction, surrounding views and the relevant outdoor-lighting source boundary.
Technical meaning
Spill light is light that lands outside the intended target area, such as beyond a driveway, yard, sign or sports surface.
Spill-light assessment depends on beam angle, aiming direction, mounting height, shielding, surface reflectance and neighbouring viewpoints.
Calculation use
Beam-angle and outdoor planning notes can flag when a wider beam or poor aim may increase spill beyond the target surface.
Spill-light notes help separate useful light on the task area from light that may affect adjoining properties, roads or sky view.
Not the same as
Spill light is not the same as total lumens. A high-output fitting can be well controlled, and a lower-output fitting can still be poorly aimed.
A simple beam estimate is not an AS/NZS 4282 assessment and does not authorise outdoor lighting limits.
Australian context
Australian outdoor lighting planning should treat spill and glare as neighbour, road-user and sky-impact issues that need project-specific review when risk is material.
Examples
Example
Value
Planning note
Driveway floodlight
Wide beam
May light the driveway well while also reaching a fence line or window.
Shielded fitting
Reduced upward spill
Cut-off and aiming can reduce unwanted light, but the surrounding view still matters.
Sports or car park edge
Boundary-sensitive
Light near property edges often needs more than a simple beam-width estimate.