I'm familiar with the basic ideas of lumen levels, throw, spread, basic LED technology, reflector/lens types etc but not really with measuring OTF lumens. Which I'm guessing is the only meaningful way to compare flashlights — ignoring for the moment their intended purpose... or manufacturer's advertising blurb.
The sort of questions I have are like do I measure the lux at 1m at the very edge of the spillbeam and at the centre of the hot spot? Or Neither? How do I measure it at a specific throw distance, say 50m? Or do I do all the measurements at 1m and then simply interpolate the result? Or am I grossly oversimplifying the use of this lux meter altogether.
Also, if there's a convenient site or page here that answers these sorts of newbie questions, then I'd appreciate it if someone here could suggest one. It'd also save you guys wasting your time explaining this stuff LOL.
The best way would be to make your own integrating sphere. Aside from that, another fairly general way to compare lights is by doing a ceiling bounce test. What you do is go to a room that has no ambient light and a white ceiling, and preferably white walls (bathrooms are usually good for this). If you already have a luxmeter, then place it on the floor with the detector pointing up. Then place the torch on the floor and turn it on while it's pointing up at the ceiling. Record the number in lux. If you don't have a luxmeter you can still perform this test by using two torches back to back...You'll be eyeballing it, but it's a good quick way to tell which torch is putting out more light, regardless of beam style. Also, if you have a good camera you can take photos of the the ceiling bounce tests, then compare them on your computer screen. Check out Foy's excellent post where he compares a few torches this way.
I find that using the room integrating sphere isn't reliable w/ the meter pointing up. Seems to vary too much based on the optics, just like you don't want the meter directly opposite of the hotspot in the sphere. So I point it at a side wall.
On some of my lower-output lights, I can stare straight into the reflector on "high" for a full second, and my vision returns in about 3 minutes.
With XM-L's driven over 2.5A, it takes about 7.5 minutes for my vision in that eye to return, but with the 1A-driven vShark, it comes back in 6 minutes. Only use one eye, you need the other for stopwatch or you won't know how long you have been blinded.
Anyway, that method seemed to work ok for me until I got my 200mW green laser, since which time I've been telling my kids I'm practicing for a pirate party with the patch.
LOL, ya know I'm just kidding, don't try that at home!
That's a CEM DT-1300/1301 (think on the Aussie page they blanked out the logo LOL!). Do note that they consistently under-read by some 10-15% in lux for LEDs, not that they purposely wanna do that, just that its calibrated to a 2856K incan source. CW LED has a drop in yellows in the spectral output. Well documented in CPF.
Look at the DT-1300, its very nearly 100% accurate for incan.
BTW when you are mentioning lux, you need to mention distance. Or you can mention Candlepower. Eg 10,000 lux at 10m = 10000 x 10^2 = 1,000,000 1 million candlepower. (a lot of those searchlight have very inflated CP figures). This gives you a very good idea on throw, though not on corona/hotspot size and characteristics.
HIDs apparently do not have so much of an issue, even for 5000K bulbs.
I just make sure the geometry is such that the meter doesn't catch any spot directly illuminated by the optics, only reflected light. When I tried the ceiling method, try on different optics would vary the readings pretty drastically (esp w/ diffusers and such).