Originally Posted by
chaadster
Can you point me towards a lumen test that compares claimed lumens?
The only one I've ever seen was on MTBR, but they seem to have taken that down, and now only publish measured lux. There's a video showing how they got measured lumens (with the collecting sphere), but again, I can't seem to find those results published anywhere on the site, even though I swear I saw them pop up a couple of, or three, weeks ago.
Maybe they found there was a critical flaw in their test; the collecting sphere did seem small to me, but I don't know much about these things, and can only speculate as to why MTBR took the results down in any case.
It does bring up the question, however, of what type of lumen measurement testing is being done when we see manufacturer claimed lumens. For example, are they actually reporting the headlight itself, or just the emitter under some other operating circumstances. Temperature, current, and placement of the light source in the collecting sphere are all variables that need accounting for before lumens can be effectively compared.
Of course, that may be the very reason MTBR dropped their lumen measurements; they simply were not indicative of anything useful. Certainly lux, if measured properly, as an intensity of light at a given point, could be more helpful to the consumer, particularly because theirs is the only measurement, and avoids the messy aforementioned business of lumen comparisons and of course, gives some measure of actual usable light output at a given distance.
So, I've heard people talk about "lumen exaggeration," but where is the proof (data) and even then, without knowing where those lumens are coming from (actual lamp assembly or emitter) and how they're measured, we can't really make any meaningful statements such as some are overrated.
Certainly standardized testing and measurement protocols for the actual headlight manufacturers is needed, because MTBR can't test them all!
The test lumens of each individual lights are still listed under each light. There is no chart or listing that show them all in one chart beside the ceiling bounce lux test. However, if you selected an individual light and click on the review, there is a heading that list the lumens tested for that particular light. Some of the light cannot be tested because of the opening of the Sphere. The larger housing or oval shape light are the one that the light cannot be inserted into the sphere opening for test. As cyccommute stated, they do test all lights they have using the ceiling bounce test and measure under the lux unit. What they are doing is using an enclose enviroment such as a room to simulate the sphere. Most of the lights are bounce off the ceiling and adjacent wall and the meter measure those lights. Although not as accurate as a sphere, it does allow for all light unit to be tested and does give a relative comparison if you are comparing one lighthead unit to another for total light output (not peak throw).