What is photometric performance?
How well a fixture delivers the intensity, the beam coverage and the colour that are asked of it, judged together.
Photometric performance is how well a fixture does its optical job. It is judged on three things together: the candela it gives at the required angles, the coverage of its beam, meaning its spread and direction, and the colour of its light, meaning its chromaticity.
The three are checked against the requirements and all three must be met. A fixture can be bright enough and still fail because its beam is in the wrong place or its colour is outside the permitted region. Performance is established by measurement, mainly intensity at a grid of angles and colour, and the results are then judged for acceptance as a separate step. It is not fixed for life: dirt, ageing and failed LEDs lower it in service, so it is checked again during maintenance.
Frequently Asked Questions
Q1What is photometric performance?
How well a fixture does its optical job: the intensity it gives at the required angles, the coverage of its beam and the colour of its light, taken together against the requirements.
Q2What are the parts of photometric performance?
Candela, coverage and colour. Candela is the intensity in each direction, coverage is the spread and direction of the beam, and colour is the chromaticity of the light.
Q3Can a fixture pass on intensity and still fail?
Yes. Performance needs all three. A light that is bright enough but has the beam in the wrong place, or the colour outside its region, does not perform as required.
Q4How is photometric performance established?
By measuring the fixture, mainly its intensity at a grid of angles and its colour, and comparing the results with the requirements. Acceptance of those results is a separate step.
Q5Does performance change in service?
It can. Dirt on the lens, ageing of materials and failed LEDs all reduce output, so performance is checked again during maintenance, not just once at installation.
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