Brightness testing - i've got some numbers...

Hello All CPFers, got a bit of a lumens quandry here and i'd like some help trying to solve it to work out what's what.

I tested five lights for brightness earlier, the test was performed in a tiny room (white-painted and tiled WC under the stairs) which is completely sealed in terms of outside light.

I used a phone that has quite an accurate brightness (lux) sensor to get quantitative comparisons of overall brightness. the phone (and thus the sensor) was left in the same position every time, and each light was tailstood in the same spot, pointing at the same area of the ceiling each time, so I am inclined to believe that the relative brightness measurements are accurate.

Now, i had planned to convert the lux-readings i got to lumens by matching a light with a known brightness to the lux-mesurement, do some division and end up with lumen readings, however, when i did this i ended up with some strange results.

The lights that i tested were:
iTP EOS A2 on high only (With Energizer L91)
L2 host with Chinese Xenon P60 Incan module
Romisen RC-F4 (Cree XR-E P4)
L2P host with Nailbender XP-G Q2 3000k 90CRI dropin
L2P host with XM-L+IlluminationSupply 8xAMC7135 2.8A driver

now, i had intended to use the Xenon P60 as my point of correlative reference, assuming that the module developed 60/65 lumens, but when i input this to Excel, i got the following results:


As you can see, the A2 on max, which should develop about 80 lumens is only measuring 37, and the XM-L driven at 2.8A is only rating 385 - much much lower than it should.

of course, this being excel, i was able to modify the comparison value to bring the other values into their expected ranges. I discovered that if i assumed that the Xenon-Incan was producing ~125 lumens (like if it was a P61 clone) then all the other values fell into their expected ranges very very neatly:


Assuming that the P60 incan is doing 120 lumens would mean that the A2 is producing very close to the 80 lumens it should, and the XM-L is doing around 800, which again, is what it should be doing. it also means that my RC-F4 (which i've always wondered about) is producing a very respectable 190 Lumens, and my Nailbender dropin is producing about 245, again, a very reasonable estimation.

Running my Multimeter across the back of the L2-Xenon-P60 shows that it's drawing 1.28A from a fresh pair of Panasonic CR123A. Whereabouts would this put this module in terms of it's output? for example, what sort of current draw does a Surefire P61 module do?

I always appreciate input/insight and people telling me i'm stone dead wrong

No-one? not even to say that my measurements look off?

Surefire are known for Under-rating their lumen outputs, especially a few years ago.

Basically your P60 will put out 60 lumens at some point in its runtime, but may well run much higher on fresh batteries.
try having a search for the term "Surefire Lumens"

there may also be a discrepancy between the P60's Surefire lumens (measured OTF) and however the other manufacturers rated lumens of their lights

I calibrate light meters and I know for a fact that they tend to be sensitive to Infra-Red, something that will be emitted more by incandescent lights than LED's. I doubt that white paint can reflect much of the infra-red emitted from the height you stood your lights at, but if your sensor had a direct line of sight with your lights, that could be part of the explanation. Then again, as already mentioned, Surefire under-rates their outputs, but double the amount sounds like a lot to me. My P60 certainly doesn't look like 120 lumens even with fresh batteries... perhaps you really have a P61 bulb or a really, really good P60??

The thing is, it's a china-clone P60 module, so i don't know whether it's a clone of the P60 or the P61. the light meter did not have LoS with the output from the light - reflection only

When my Surefire C2 arrives, i'll repeat the test with that, hopefully that will give a more accurate point of comparison