[PART 2] Official BLF GT Group Buy thread. Closed, but Public sales open!

Yes. I double checked to make sure.

Was there any difference between hi and turbo?

We know the GT driver puts out 2.5A and the reflector and lens are a fairly constant percentage of loss. One actual variable is the emitter. Even though all the GT’s use a D4 bin, Cree allows for a 14% tolerance in output.

So as long as your batteries are good enough to keep the led in the regulated output mode (2.5A) all the GT’s should measure within 14% of each other.

The TN42 only puts out 2A to its xhp35-HI, so it’s strange it would measure a higher lumen output.

I’ve got a TA Lumen tube, but the GT is too big to fit the opening. I can swap a smaller reflector on it and measure 2200 lumen, but that should be a little on the high side as the big stock reflector has a bit higher loss. So a would put it closer to the 1900 range.

Most other people measure about 1800 to 2000 lumen.

Another variable is whether your lux meter is sensitive to different color temps. A lot of them are less sensitive to warmer tints. If your TN42 is CW, then your meter is going to automatically read disproportionate high compared to the NW led in the GT.

The biggest variable is of course how you measure it. You would need to tell us in detail how your measuring your lights.

MRsDNF - That’s interesting, and I’m glad you brought that up. I just tested that, and came up with 1430 lumen for (double click) turbo, and 1344 lumens for “press and hold” full brightness. The time between the two test might only represent voltage drop, as I used the same charge.
What does that mean?

JasonWW,

Thanks for your response. I’m using a 180 degree bend 7 inch PVC pipe setup, meticulously sanded on the inside, with a clean, scratch free plexiglass window silicone glued in place, and calibrated for margin of error to 2 known value flashlights in 2 settings each, and averaged. I use white cloth packed around the reflector head during testing. It’s the best I could come up with without going nuts.

So far, I’ve tested 32 flashlights with this. One that I trust is an Olight Valkyrie which was rated for 400 lumen, and tested to 399. Another is a Thrunite TH10, which is rated for 825, and tested showed 903. My BLF Q8 tested to 5076. Solarforce and other oddball brands usually test far below rated lumen values. I don’t trust those ones.

On lights, I use VTC4 or Samsung 25R from known good suppliers, and I have heaps of them. (The GT blinks out 4.2v, prior)

You’re probably correct about warmer light, but I most always choose 4k-5k light on flashlights. I dislike blueish light.

The meter I’m using is a Dr Lux LX1330B, and the window on the other side is cut to match the size of the light collector on the meter, which is fixed in place during testing.

I have not conducted a beam test on the light at range, because I stopped as soon as I got the low reading, double and triple checked, and then came straight here to ask for advice.

My setup is very similar to this guy’s setup. How to measure Flashlight Lumens and Candela using ANSI/NEMA FL1 standards. - YouTube

I have found a Problem with my Lumenbox. Throwers and extreme High-Lumen Lights shows too less Lumens on the higher output levels. I compared the lower levels with new readings in my guests toilette and calculated the higher output levels with this. Afterwards my readings were near other readings.
Perhaps you have a similar problem.

I have measured 1925 Lumen with changed LED (XHP35 HI E2-3C) and without Reflector on my Lumenbox. Reflector is too big for me, too.
Mostly, my readings are on the lower end, but I think my box is good calibrated.
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Edit:

With dead Emitter (one dead die), I have measured 1400 Lumen (without reflector) and 1270 Lumen on max ramp (without reflector): BLF GT official support thread [FAQ updated 11 Jan 2018] - #145 by Wieselflinkpro

Just a bunch of notes:

Advanced Knife Bro is Mhanlen on BLF.

Just an open tube like that can cause throwy lights to read a bit higher than floody lights. They don’t really seem to diffuse the beam.

If you want a reference light to calibrate your own lumen tube, Maukka is selling some. More details here.

Okay, back to your situation:

Even if your lumen tube and calibration were off, I would still think the GT would read higher output than the TN42. Is your TN42 also NW?

One thing I’ve noticed about the GT is that it’s huge reflector moves the led a lot further away from the lumen tube opening which reduces brightness in the tube.

Also, the large reflector tends to absorb more of the leds output than a smaller reflector.

Maybe if we could measure the raw leds or use the same reflector on both lights, we would see the GT have a bit higher lumen output.

The bottom line is it’s a difficult light to measure lumens on.

There shouldn’t be any doubt the GT throws further. The TN42 is in the 600kcd to 700kcd range and the GT should be in the 1mcd to 1.3mcd range. I would go ahead and measure that. If you see this same big gap then your GT is doing higher lumens than your lumen tube is reading.

I decided to measure my GT lumens 3 different ways using my TA Lumen Tube (.68) which only has a 3.5” opening.

First is to just overlap the light on the tube. This blocks a lot of the output and is not accurate at all.
High 1130 lm
Turbo 1250 lm

Next I removed the reflector and stuck the lower head into the tube. Also very inaccurate.

High 1290 lm
Turbo 1420 lm

Lastly I used an OP reflector from an L6 (no lens, which might make my reading 3% higher) and got what I think is a pretty realistic number.

High 2000 lm
Turbo 2180 lm

I’m pretty sure a lens and the stock reflector would knock down the turbo to under 2000 lumen. Once I get my calibration light from Maukka I’ll temporarily adapt a larger opening to the TA Tube and figure out the multiplier number. Then hopefully I can measure it with the stock reflector and lens. At least I hope I can.

Anyway, this just goes to show how difficult it is to measure lumens when you don’t have a $10k+ professional integrating sphere.

JasonWW - Thanks! I can’t tell you how much I appreciate the help.
The TN42 measured 15700 lux when I measured it.

Do you know what the voltage at the emitter should be? I managed to get the head off the thing last night, and it’s 14.9v on “high” and 15.65v on “Turbo,” at 0.23A DC. Is that correct?

I took your idea with the short reflector, and used aluminum foil with a hole cut in it, and the emitter directly over the pipe, and the best I could manage was 1501 lumens.

What do your throw numbers show at 10m with the GT?

Are you realy shure that all dies on the LED are ok an not like mine in the pictures above?

I checked my voltage and yours is higher than mine. I got 14.6v on high and 15.3v on turbo.

To check the amperage you would need to unsolder one of the LED wires and either extend one and use a clamp style ammeter or you could put a multimeter style ammeter inline with the two wires. The clamp style is usually more accurate. You should be seeing around 2 amp on High and 2.5 amp on Turbo.

Do you know how to measure the candela at 1 meter?

1 meter is not nearly enough for the GT, 10m is much better and makes the math easy as well.

Oh that’s s pulse modulated driver, isn’t it?

Texas_Ace - That’s a good idea. I will do 10m as requested. Here is the result of that test:
10m = 10.9 yards = 32.8ft. I got 10500 lux, (double click turbo) centered on the collector.
Does that sound correct?

Wieselflinkpro - Yes. I’m sure. If I put the light on moonlight, I can look at it, but I wish I had some welding glass, so I could look at it on Turbo.

JasonWW - Yes, I did de-solder one of the wires, and I double checked my meter was on DC. I have a Fluke 87v. But, like I said, that’s a pulse modulated driver, isn’t it? I’m not going to get an accurate reading unless I record it and measure the pulse widths, right? The duty cycle.

You misunderstand. We need to know the candela at 1 meter. To get this number we do the actual measurement at a longer distance (5m, 10m, etc…) then calculate it back to 1 meter. I was basically asking Longtom if he knew how to do these calculations.

Yes, that sounds spot on, that is 1Mcd which depending on the conditions is what I get out of mine as well.

Ah, Ok that makes more sense. I figured you knew that 1 meter was not enough.

Texas_Ace, (and everybody else)

ALL IS WELL! Thanks to everybody for the help, and for the lessons learned. Every time I come here, I learn something new. That’s what makes this forum so wonderful.

Well, Jason did the real work, I just repeated what he said lol.

TA, you can remove my name from the missing bag list. Neal refunded me since it never came. Thank you.