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

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.

I’m not sure what you mean by “centered on the collector”.

I measure out my distance from the sensor on the wall to the emitter. I turn the light on turbo and then go to the wall and move my lux meter around in the hot spot to find the brightest part of it.

To calculate your 10,500 lux back to 1 meter you go 10500 x 10 x 10 = 1,050,000cd.
To find the throw distance to take 1,050,000 x 4 = 4,200,000. Then find the square root of that and you get 2,049 meters of throw or a bit over two kilometers.

This sounds right in line with other people’s measurements.

I’ve heard some people get slightly different results with the GT if they measure it at 15 or even 20 meters. It seems to depend on how the beam is focused.

You can also try measuring the TN42 at 10 meters and see if it’s around 6,500 lux. I think that’s what it should be close to.

Okay.

Also, I still have not heard anything from Neal or Leo about the Issues list. Does Leo exist? :slight_smile: I’ve never heard anything from him.

On this I have no idea. I would assume it would read normally. Some DMM just don’t read amperage accurately due to resistance in the leads and connectors. I always use a clamp style ammeter.

It means with the center of the hotspot of the beam centered directly onto the light collector (the sensor thingy) of the meter at the requested 10 meters.

No, that’s not such a good idea. The very center of the hot spot can sometimes be the dimmest area. Look at this pic of my L6 and you can see the center is definitely dimmer.

The GT at 10 meters might be a different story, but I would still move the sensor around to find the brightest part of the hot spot.

I have got 1700 lumen with the TA tube… it could have been around 2000 lumen if the light doesn’t escape from the opening…

So yea … blf gt is doing around 2000 ballpark.