Truly awesome Lux numbers, looking forward to seeing pics of the light and set up.
For what it’s worth, Canon is a registered trademark of a camera company, your use of the word would be cannon, as in long thrower. (just a bit of OCD coming through, right is right, after all)
Wouldn’t a light “cannon” project a large diameter beam, like the old aircraft search lights? Maybe I need coffee… sorry
Wow!! Congrats on this site unseen project! Try a reading at 10-15 meters, betcha you will get over 1.5 easy... I think every light I've tested at 5m got a nice little bump at ~12m, plus it's actually more accurate.
Sk68 died a smoking blue death (single mode with liion cell) so I pulled out the pill and reamed the hollow shell to the OD of 1/2” copper pipe(.625”). And made up a copper insert. I might go old school and direct solder an XRE since a sinkpad would raise the die out of focus.
Thanks guys I actually made a mistake in my calculations, there’s a thing called etendue, and due to this the formula 1/r^2 doesn’t directly apply to my light because of how it is almost collimated…
The farther I take the measurement from the light, the more lux @ 1m I get.
The correct way to calculate it is by using this tool: Candlepower & Divergence Calculator For Uniform Beam Lights or you can do a bit of trig to manually figure out the distance behind the lens
This means that I’ve always been underestimating my measurements, and I might be getting actual candlepower in the tens of millions….
I need to make new measurements at a longer distance, and measure the diameter of the spot to figure out the real number, so hopefully in the next week I can actually tell you guys the real numbers
Yes, but there are so many “light cannon” named lights I wanted mine to show up on google search, so I named it “lightcanon flashlight” so that it is pretty much the first result
The XP-Ls are new cree production. with the really low Vf, so pretty much any bin in direct drive will die from too much current.
You need to use a current limiting driver for these, not FET or DD
This is interesting. The details of this are not often discussed. I think for largish diameter lights this definitely makes a significant difference in how we would calculate the throw (cd).
I think you explained it fine; this is just some further explanation of my understanding of the subject. The inverse square law, which we use to calculate the cd, is valid for a point source of light and the distance in the formula should be from the point of light to where you measure. With flashlight beams, the light appears to come from a point behind the flashlight, not the face of the flashlight, and so this effective distance should be used in the formula, (cd)=(lux)(d^2), instead of just the distance to the flashlight.
Something bothers me about that calculator you linked, though. It implies that (with all other things the same) the size of the emitter affects the divergence distance behind the aperture. This somehow doesn’t seem right to me. I did some quick tests with my UF 1504 lens light. To get a more accurate measure of this effective divergence distance, I measured the beam size at different distances (2.5m, 4.2m, 10.2m from the lens), then simply graphed the points and drew a line through them. The point at which the line crosses zero is the effective point from which the light is emanating. I did this with two different sized emitters, the dedomed old XPG2 and the XPL HI, and got equal divergence distances behind the lens, 2.5m. This means, effectively, that the beam size is not the size of the lens at the lens. Anyway, I don’t understand all the implications, just wanted to put it out there.
They were XM-L2’s that died, but when I reported it I realized that it wasn’t just me, U3’s were dying for everyone. So I was wondering if there is a similar “cursed” bin of XP-L’s
It’s not the size of the emitter that matters, it is the size of the aperture of the flashlight.
I actually didn’t know how the website algorithm worked, so I took out my trusty calculator and did some simple trig, and I did get the same value as the website.
Basically imagine a triangle, starts at one point, and at 10m has a spot that is 10cm.
That is far more divergence than a rhombus that starts at 5cm and at 10m has a 10cm spot. (which is a section of a much looonger triangle)
As you can see, the second case has a lot less divergence than the first.
The square law of light “calculate back to 1m” method works for case 1 but not case 2.
I will draw a pic later today to illustrate this for other people