I just finished building a rig for reflector testing.
It consists of 1) a clamp in which a reflector can be clamped in a fixed position of 7 meters from the wall/luxmeter (the longest distance I can cover in my living room), 2) a double constant (within 0.3%) output lightsource at 350mA, bare leds soldered onto a copper pillar: 1x XM-L2 (cool white) of 180 lumen, and 1x dedomed XP-E2 (cool white) of 120 lumen, and 3) an xyz-stage that can position the lightsource in a controlled way in three axis, to easily position the light source in a 'perfect' focus in the reflector.
With this set-up I can measure and compare the throw of any reflector (and lens) using the exact same lightsource and output every time. Only the getting the best focus is a tricky manual thing, I think I will improve on that over time. On an incidental basis I will add measurements to this thread, building the set-up was more fun than actually doing tests . And I do not have a that extensive collection of reflectors, and some are dusty/scratched/dirty. When data are being collected, I can even give an idea of throw quality: kcd/cm2 front surface area, for any given reflector.
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Oct 20th Test of three C8 reflectors of the same dimensions that I had around: an aluminium OP-reflector and an aluminium smooth reflector, both from Fasttech, and a plastic one (came out of a budget flashlight, can't remember which one). All had some dust, and the alu smooth one had a slight deposit in the deep part (not that important for throw) only visible with the led lighted up inside.
throw with 120 lumen dedomed XP-E2 (kcd) | throw with 180 lumen XM-L2 (kcd) | |
plastic smooth C8 reflector | 42.7 | 5.7 |
aluminium smooth C8 reflector | 41.7 | 6.3 |
aluminium OP C8 reflector | 17.8 | 5.7 |
That plastic reflector works fine, even though you can see while focussing that it is not perfectly round, the amount of reflection may make up for that. And that an OP reflector throws about as well as a smooth one is correct for bigger leds, but it fails to throw with a small led.
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Dec. 28th 2015
I dressed up my reflector test rig tonight (I'm allowed 2 square meter of permanent hobby space in the house, so part of my rigs must be dismantled after each use) and tested the X6 and D80 reflector. Because I wanted to know for these two flashlights in the same category, separated from all other parameters, which reflector in principle was the better thrower: the odds were at the D80: larger diameter, smoother surface finish.
I'm getting quite a good feeling for finding the best focus for each reflector, so with more reflectors tested the numbers are getting pretty accurate. The test leds are a dedomed XP-E2 and domed XM-L2, both cool white, both constant output at 350mA. Throw is measured at 7 meters, numbers were calculated back to kcd. Here you go:
reflector | XP-E2 dedomed at 350mA | XM-L2 at 350mA | remarks |
BLF X6 reflector | 21.2 kcd | 3.79 kcd | diameter=29mm |
Lucky Sun D80 reflector | 29.4 kcd | 4.71 kcd | diameter=33mm |
So indeed the D80 reflector is the better thrower, for the dedomed XP-E2 the throw is 39% more, for the XM-L2 the throw is 24% more. The actual throw from the whole flashlight is dependent on many more things, I just wanted to single out the reflector.
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