A photobiological hazard in which intense short-wavelength light, peaking in harm around 435 to 440 nm, damages the retina through photochemical reactions rather than heat. It depends on source radiance and exposure time, so it matters for staring into bright, small sources rather than for ordinary room light. It is assessed under photobiological safety standards and expressed through risk groups.
Bare COB in that luminaire tests at the edge of RG2 for blue light hazard, so it needs a diffuser or a warning label.
Also heard as
- BLH
- photochemical retinal hazard
Do not mix it up with
- Melanopic EDI: Melanopic metrics describe non-visual circadian effects of light, not eye damage; the two use different spectral weightings.
Related terms
Risk group
The photobiological safety class of a lamp or luminaire, from RG0 exempt to RG3 high risk.
SPD
Spectral Power Distribution: a graph of how much power a light source emits at each wavelength.
COB
Chip-on-Board: an LED array with many dies mounted closely under one phosphor layer, acting as a single compact source.
Radiometry
Measurement of optical radiation in physical energy units such as watts, without weighting for human vision.