You know that in the lighting industry there are many standards and common criteria to judge a lamp. But unfortunately this is insider jargon and they don't always share these figures since it is meaningless for 98% of the people.
For instance the Life time, lumen maintenance and failure rate is a very good and important one:
Life time, lumen maintenance and failure rate
The L value: the light output of an LED Module decreases over the lifetime, this is characterized with the L value. L70 means that the LED module will give 70 % of its initial luminous flux. This value is always related to the number of operation hours and therefore defines the lifetime of an LED module.
As the L value is a statistical value and the lumen maintenace may vary over the delivered LED modules.
The B value defines the amount of modules which are below the specific L value, e.g. L70B10 means 10 % of the LED modules are below 70 % of the inital luminous flux, respectivly 90 % will be above 70 % of the initial value.
The C valueThe percentage of failed modules (fatal failure).
The F value is the combination of the B and C value. That means for F degradation complete failures are considered, e.g. L70F10 means 10 % of the LED modules may fail or be below 70 % of the initial luminous flux.
So a ledmodule in a fixture with a given L60F50 at 30000 hrs means that 50% of the leds on the ledmodules in the fixture wll have less than 60% of their initial rated luminous flux left.
So to judge what you want to buy this figure is as important as how many lumens/watt you will get.
A flashlight (the ones that flash one times) have an enormous amount of lumens/watt but it lasts only a tenth of a second.
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