A lumen maintenance rating describing when an LED source or luminaire reaches 70 percent of its starting output, the level at which the loss becomes noticeable in most applications. Values come from LM-80 test data on the LED packages extrapolated with the TM-21 method, which limits projections to six times the test duration. L80 and L90 are stricter versions; B10 and B50 add what fraction of units fall short.
They're claiming L70 at 100,000 hours, but with 10,000 hours of LM-80 data TM-21 only lets you report over 60,000.
Read the fine print on lifetime claims: any number beyond six times the LM-80 test hours is marketing, not TM-21.
Also heard as
- L70 life
Related terms
LM-80
The test method for tracking how LED packages lose light over time, the basis of lifetime claims.
Junction temperature
The temperature of the active semiconductor region inside an LED, which governs its output, color and lifetime.
Light loss factor
A multiplier, usually 0.7 to 0.9, applied to initial light levels to predict what the system delivers after aging and dirt.
LED
Light-Emitting Diode: a semiconductor light source, made white for lighting by coating a blue chip with phosphor.