A motorized system that records luminous intensity over a grid of angles around a luminaire, at a distance long enough for the source to act as a point. Type C goniophotometers, with a vertical axis, serve most interior and street luminaires; Type A and B suit floodlights and vehicle lamps. Mirror goniophotometers swing a mirror around a fixed luminaire. The result is the candela table that becomes an IES or EULUMDAT file.
Goniophotometer run on the new street head takes six hours at 2.5 degree steps, so it won't have an IES file until tomorrow.
Also heard as
- gonio
Related terms
IES file
A standard text file of a luminaire's measured candela distribution, loaded into lighting calculation software.
Luminous intensity
How much light a source sends out in one specific direction, measured in candelas.
LM-79
The standard method for measuring a complete LED luminaire's light output, power, efficacy, color and distribution.
Integrating sphere
A white-lined hollow ball that spreads a source's light evenly so one detector can read its total lumens and color.