Lumen of LED light is various depending on which values are being quoted, more detailed information of which is as followed that could help choose the right LED light for the right application.
Raw Lumen is the theoretical output of a light, which is result of multiplying by the theoretical output of the unit LED by the quantity of the LED chips in a light.
For example, 8LEDs rated at 100 Lumen/watt, the Raw Lumen of which is 8×100 = 800 Lumen.
While the Effective Lumen is the actual output of a light, which takes electrical and other losses(such as thermal, optical, assembly) into consideration. Therefore it’s a better result revealing the actually produced light on visual effect.
For example, the Raw Lumen of a light is 800 while the thermal, optical and assembly losses take 20% of the Raw Lumen, which means the Effective Lumen is 800－160 =640.
By the way, what that thermal, optical and assembly losses mean?
In general, they are inherent losses come with any lights, which mainly related to these 3 items: thermal losses, optical losses and the assembly variation.
The LED chips produce less light as their become hotter, in a relatively small area they generate a specific amount of power. As the LED chips are powered for longer and longer, they are typically becoming hotter up to the thermal management system, which is quite usual for the LED chips to reach more that 100℃.
For vehicle applications, most lamps are required to be measured at 10 and 30 minutes to make sure that the temperature of the LED is stable then, which results in the LED produces less light of about 10-20% than the advertised value.
About optical and assembly losses:
As light travels through an object, it loses intensity depending on the clarity of the material, which is caused by the inherent losses internal to the material and losses around the edge of the object as the light travels from air, through the object, and back into to air. The losses can vary from 10-20% due to the material of the object whether the light source is an LED or a bulb.
There are always losses with the assembly variation while manufacturing. The output can be various as the assembly tolerances that could affect the overall performance from the theoretical ones.