Photometrics are measurements of light output and distribution, weighted for human visual response. A fixture’s published data may include illuminance tables, luminous intensity curves, total luminous flux, beam angles or an IES photometric file.
Compare the same conditions
For a lux comparison, match the distance, CCT, output mode, dimming setting, modifier and measurement position. A bare-head measurement and a narrow-reflector measurement describe different arrangements. Centre-beam output also says little about how evenly a fixture lights the rest of the frame.
Practical example
A reflector can raise centre-beam lux while narrowing coverage. If you need to light a wide diffusion frame, the stronger centre reading may be less useful than an even beam across the material. Read the beam information and test the complete setup.
Using published data
Photometrics help estimate a starting position and compare documented configurations. Distance scaling is most reliable when the source behaves approximately like a point source at the measurement distances. Photometric output does not establish colour rendition, flicker performance or the exposure your camera will produce under every spectral condition.
Equipment examples
The Aputure LS 600x Pro entry separates documented output configurations so the reflector and measurement conditions remain visible.
Related terms
Lux · Candela · Beam Angle · Field Angle · Inverse-Square Law
References
IES: measurement of light · Aputure: LS 600x Pro photometrics