It’s going to be interesting to see how a real “sphere” compares to my 4” PVC trap box. The PVC box was calibrated to 20 something known name brand lights with ANSI ratings, it’s been very comparable on some lights and not so much on others. At least this will give me an ability to average out results.
I started to get a UCLp lens from Chris to replace the glass shelf in this box, figured that would have to matter, but never followed up on it. It matters in a flashlight, sometimes it matters a LOT, so the glass shelf has to be reflecting a bunch of light back towards the light and as such, skewing results. Need to go ahead and get the big 4 1/4” shelf replaced…
So I have calculated the lumens I expect from each mode of my BLF A6 and I intend to use those numbers for the factory calibration. But does anyone know a service that I can send my flashlight to so we can get an official output?
Just sent the extra $22. Would be great to get some kind of more certain calibration than just using listed specs. I’d be willing to wait a bit longer for that, even if it were just sending to a member who has a well-tested sphere or lightbox to cross-check your numbers.
Thanks SawMaster. Yes I agree we want to do one or the other. I haven’t seen a BLF member say his sphere is calibrated any other way than the same calculations though. Remember too that we can change the app anytime.
I’m not sure if the BLF-A6 is such a good light to do the calibration with, the output on all but the three lowest modes are dependent on just about everything because they use the FET which is a direct drive situation. You want a light that has a constant output, as independent as possible of battery type, battery drainage, temperature, the random resistance of the switch each time it is switched on etc. In other words: a well-heatsinked, low output, current controlled light, which the BLF-A6 is pretty far from but on the lowest few modes, but you may not want PWM too. One of the Convoy lights could be a candidate, with less 7135 chips than they come stock, perhaps only one or two. Or some of the top-brand lights come with very good current regulation and constant output, usually not on the highest mode but one of the medium modes. Selfbuilt’s reviews at CPF show which lights are candidates, UPz provides decent output charts with his reviews too.
I know a service in the Netherlands that does calibration, and it is $350. I hope there’s a cheaper option over in the States.
Would it be wise to calibrate the meters/spheres against some already known production lights with published ANSI/NEMA FL-1 test data? There should be plenty of potential candidates, and I would think cross-checking with a few different lights from different manufacturers that adhere to that standard would be a good idea. Just my $.02.
I don’t have a ton of lights but the ones with the most reliable outputs I have are probably my zebralights: sc52fw and sc32. I’d be willing to ship you one if that’ll help. You can ship it back with my sphere.
If you are asking if my specific lights have been measured or documented in any way then I sheepishly apologize, for they are not. I am a certified Zebraliever ™ so I take all numbers on the holy spreadsheet as gospel.
I’ve heard the Zebralight is pretty consistent with their ratings, so that would be a good start!
Just remember to adhere to the standards/conditions as much as possible when checking a known (ANSI rated) light’s numbers against the meter/sphere calibration.
Use same type of battery (primary vs. rechargeable) that the light was intended for and rated for.
Take readings after 30 seconds of run time.
Measure peak beam intensity at 2, 10, or 30 meters away (depending on the size of the light), and calculate back to 1 meter via inverse square law.
Beam distance = square root of (peak beam intensity divided by .25).
Those lights can work for the low end, but we really need checkpoints all along the operating curve. You wouldn’t be able to trust it otherwise.
We need to test as many sample points as possible over as large of a range as possible and plot them in Excel. Then use the curve-fit tool to give us the equation to plug into the app.
You do not necessarily need calibration over the whole output range, as far as I have noticed, even though my test on that was not great, even cheap luxmeters have a nice lineair response to brightness.
Wondering aloud if someone has a contact at Streamlight, Zebralight, or another ANSI-compliant manufacturer who could get light(s) which they have actually tested the output of to JoshK?
So wait, are we assuming that all these meters will read consistently just because they’re bought from the same place at the same time? That doesn’t seem very likely to me. They’re still cheap Chinese meters. It would be best for each individual meter to be calibrated in its matching sphere, right? Yes that means each sphere/meter combo will have its own fitting equation, but that’s really the only way to get it right, isn’t it? Or am I missing something?
Maybe that’s why I never understood why I shouldn’t just send my existing meter. I didn’t know we were trying to do a single calibration that would apply to all the spheres.
As for calibration, I also own a lot of lights. I can send along another Zebra or two if you’d like (I’ve got 11). They’re supposed to be very close to the rated output. I think it would probably be best to mix in some other types of lights, like small throwers (EagleTac DX30LC2?) and some larger lights too, (Nitecore TM16w? Thrunite TN35? Olight M3SX-UT?). I have these lights and others in unmodified factory form and am happy to loan them for testing.
