From the customer survey report, many customers are easy to confuse LM80, LM79, and L70 or assume they test the same measure in an LED product. Although all of them are used when discussing LEDs, they are not related measurements.

What is LM-79?

It is the Illuminating Engineering Society of North America (IESNA) approved method for the Electrical and Photometric Measurements of Solid-State Lighting. It measures an LED luminaire or integral lamp as a whole system according to a standard process using specified equipment. The "LM-79-08 Approved Method: Electrical and Photometric Measurements of Solid-State Lighting (SSL) Products" test allows an end user to evaluate the suitability of the solid state lighting system, for instance a lighting fixture, for its use in a specific application or to compare SSL systems with one another. LM79 provides data for total luminous flux, electric power, and efficacy and chromaticity.

What is LM-80?

LM-80 is measuring Lumen Maintenance of LED light sources.

Which is refers to a method for measuring the lumen depreciation of solid‐state light sources, such as LED packages, modules, and arrays. Before the advent of LM-80, LED component manufacturers each reported lumen maintenance data using their own disparate and varied systems.To avoid customer confusion, members of the Illuminating Engineering Society (IES), came together to create a standard methodology that would allow customers to evaluate and compare the lumen maintenance of LED components from different companies. LM-80 was born.It was developed by the Illuminating Engineering Society of North America (IESNA), to allow people the ability to evaluate and compare the lumen maintenance of LED components from different companies.It is typically a 6000hr test (can be 10,000hrs) that shows depreciation and chromaticity shift over the period at particular operating temperatures 55 degrees, 85 degrees, and a third manufacturer defined temperature, say 105 degrees.

What is TM-21?

TM-21-2011 (Projecting Long Term Lumen Maintenance of LED Light Sources), generally known as "TM-21". It is the Illuminating Engineering Society of North America (IESNA) approved method for taking LM-80 data and making useful LED lifetime projections. The standards apply to lifetime projection of LED package, array or module alone. The results can then be used to interpolate the lifetime of an LED source within a system (luminaire or integrated lamp) using the in-situ LED source case temperature.Light output is measured at a minimum of every 1,000 hours over a minimum period of 6,000 hours use. TM-21 introduced the use of "L" values such as L70, L50, L30, etc.