Lighting Glossary

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LM-79 Electrical and Photometric Measurements of Solid-State Lighting Products

An IES-approved method to quantify the performance of the fixture’s total luminous flux, luminous efficacy (l/w), luminous intensity (candelas) and chromaticity, CRI and color temperature.
This method specifies that products should be tested with absolute rather than relative photometry. Absolute photometry takes into account the performance of the LEDs as used in a particular fixture in its production configuration. The impact of the fixture’s orientation and thermal management is accounted for in this method.

LM-80 Measuring Lumen Maintenance of LED Light Sources

An IES-approved method to determine the lumen maintenance of LED light sources.
The LED manufacturers provide life ratings for individual LEDs at specific drive currents and operating temperatures.
In turn, the luminaire manufacturer measures the drive current and temperature in the LED fixture. The data is crossed to estimate LED life in a fixture.

L70 is the life at which the fixture delivers 70% of initial light output.