What's LM79 LM80 ISTM & TM21?  (reprinted from www.lightlabint.com)

LM-79 is an approved method by the Illuminating Engineering Society of North America (IESNA),for taking electrical and photometric measurements of SSL products. It covers total flux (light output), electrical power, efficacy, chromaticity, and intensity distribution. The five required metrics on the LED Lighting Facts label come from LM-79 test results. Testing can only be completed by an EPA-Recognized Laboratory. 

The ISTM test measures the operating temperature and drive current of the LEDs inside the luminaire as would be encountered when the luminaire is normally used ("In-Situ"). The LM80 report specifies the location of the Temperature Measurement Point (TMP), the same point is measured duing the ISTM test. The Standard prescribing the luminaire conditions during the ISTM test is UL1598 in the USA and AS 60598.1 in Australia. The TMP temperature and drive current must be below that in the LM80 report for the LM80 results to be applicable to the luminaire.

LM-80 Reports and Driver Spec sheets are needed to complete this test and determine Tc locations.

The North American IES standard LM80 prescribes a test method whereby a batch of LEDs are mounted onto a carrier and are tested at a specific drive current and ambient temperature. At intervals during this test the luminous flux, CCT and other metrics are measured. Three ambient temperatures are used in the test: 55°C, 85°C and a temperature chosen by the LED manufacturer. The samples are operated at these temperatures and at a specific drive current for a period of 1000hrs, then the LEDs are removed from the oven, allowed to cool to 25°C ambient and their light output characteristics are measured as per the LED manufacture's specified method; typically by energising the LED for a short interval between 10 and 20 ms. The LEDs are then placed back in the oven and the process repeated for a minimum of 6000hrs (approximately nine months).

Once the LM80 test has concluded, the measurements are used to determine a depreciation curve for the luminous flux at each temperature. The data is extrapolated using the method described in the North American Technical Memorandum TM21 to determine the "Lumen Maintenance Life Projection (Lp)". The end point of the extrapolation is typically 70% of the initial light output. There is a spreadsheet calculator available at the www.energystar.gov website to perform the calculations.