Every optic — reflector, lens, diffuser, or louver — absorbs some light while shaping the beam. Optical efficiency is the share of source lumens that actually leaves the fixture.
| Optic type | Typical efficiency |
|---|---|
| Specular reflector | 85 to 92% |
| Faceted reflector | 80 to 88% |
| TIR lens | 85 to 92% |
| Prismatic lens | 75 to 85% |
| Frosted diffuser | 70 to 85% |
| Deep-cell louver | 55 to 70% |
Efficiency vs control
There is always a trade-off: the optics that control glare best (louvers, heavy diffusers) also lose the most light. Clear reflectors and TIR lenses keep efficiency high but offer less glare softening.
Account for optical efficiency when comparing fixtures — a high-lumen source behind an inefficient optic can deliver less to the task than a modest source behind a clean one.
See the Lens Material Properties and the Reflector Beam Comparison.
What optical efficiency means
Every optic — reflector, lens, diffuser, or louver — absorbs some light while shaping the beam, so a fixture delivers fewer lumens than its raw LED produces. Optical efficiency is the percentage that makes it out. Clear reflectors and simple lenses are the most efficient (often 85–95%); frosted diffusers and deep louvers trade more light (sometimes 60–80%) for glare control and a softer, even appearance. When comparing fixtures, look at delivered lumens (after the optic) rather than raw LED lumens, since that’s what actually reaches the room. A less efficient optic can still be the right call when glare control or beam quality matters more than raw output.