Photometric testing standards first appeared in the late 1800’s; they were needed by the emerging gas lighting industry. Later standards focused on electric illumination. The traditional standardized photometric testing methods in use today, Commission International De’Leclairage (CIE) 127 and Illuminating Engineering Society of North America (IESNA) LM-79, were originally adapted from tests for incandescent lamps and other electric lamps. In these testing methods, the lamp is powered continuously and long stabilization times are mandated.
Though tedious, these methods worked well for low power LED devices targeting indicator applications, but the long stabilization times were impractical in many applications – for example for production LED testing. More powerful LEDs were also difficult to test because heating caused significant LED temperature rise, altering the results. Many laboratories substituted ad hoc pulsed methods to speed testing, but often absolute accuracy was sacrificed and method variations meant results from different laboratories did not agree.
For more see Photonics Spectra May 2015 article: Improved Photometric Testing for High-Power LEDs
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