Integrating lumen tube attempt

Hi all,

I bought myself a light meter as I wanted to have a go at measuring the output of some of my modded lights. Here is what I came up with:

I have 4 lights with known outputs that I attempted to calibrate with - an Olight S1 Mini Baton, Olight M2R Warrior, Fenix PD35 (2013) and ITP A1 EOS.

The problem is they don’t all give me the same multiplier when I get their lux readings by using my contraption. I get 0.20 with my Olights and 0.30 with my Fenix. After some averaging by measuring my other lights I reached a rough multiplier of 0.23 which seems to show representative results for some of my lights, it massively under-displays the Olights.

The only thing I can think of is it’s a bit smooth inside (needs sanding), there’s a bit of light bleeding through the PVC (needs painting?) and there are some square edges where the size of the tube increases toward the middle. I’m thinking of taking it apart and cutting it in the middle and joining the thinner pieces together so it’s just one thickness all the way through.

Anything else anyone can think of? Any tips from building your own?

Thanks!

Don’t just go off manufacturer specs, order some calibration lights from maukka. Well worth the expense if you care about accurate measurements.

If you are worried about the integration properties of your lumen tube, I would recommend diffusing the light at the input port. Next step is ensuring the inside is not reflective. Some bleeding through the tube doesn’t really matter since that is linear between all lights. Then it’s a matter of getting something to calibrate against. If still worried about how the tube reacts to throwy and floody lights, preferably using both sorts for calibration.

My son and I built mine yesterday. A welcome upgrade from the previous lumen measuring contraption, ye olde integrating foam cooler!

X2

My sphere calibrated Convoy S2+ from maukka was within 1 lumen when measured with my Texas Ace Calibrated Lumens Tube.

Thanks guys, I’ll consider the calibration lights if I can’t get anywhere!

I made some changes to the tube last night…

I also added a piece of paper in the middle of the tube to diffuse the beam, but my results are still a little inconsistent. Warmer tints are a different multiplier (is this normal?), and although my Fenix PD35 and Olight S1 Mini Baton are exactly the same multiplier, my BLF A6 seems to read for example quite high, and my Astrolux C8 ironically is quite close to the Fenix and Olight. My NW M2R Warrior is the furthest from the rest, even taking into account Maukka’s results with that light.

Do I need more bends? More diffusing? Both? Set fire to it and just buy a TA calibrated tube?! Should I just accept that this is as good as I’ll likely get it and take the different multipliers into account with cool and warm temperatures?

4 inch Schedule 80 P-Trap , One 90 degree elbow with glass glued in at the shelf , NO diffuser film , NO pieces glued inside …. just some simple parts. Some foam with various sized cut outs for different sized lights to block any escaping light , a cut out for the headlamps / 90 degree lights , figure out the multiplier you need for your tube and off you go. (pictures below)

My test results compared to Maukaa’s test lights?…………….

Maukka……… BLF 348 … 56.1 lumens at start … 55.3 at 30 …. 54.3 at 60 sec …

My results … 58 lumens at start ……….54 at 30 sec …… 53 at 60 sec

Maukka S2+ …. 290.8 at start …. 290.8 at 30 sec ….290.5 at 60 sec

My results …… 285 at start …. 284.5 at 30 sec …… 284.5 at 60 sec

As you can see my light tube is pretty close to what Maukka test lights are and I have always been fairly consistent with the factory ANSI readings from the big name manufacturers with this set up.

I am no where near the 20% to 30% (over) difference that had been suggested a few times by a few in the forum with my meter. I am actually slightly under the test lights with my setup.




One question: How did you learn the “known outputs” of the 4 lights??

For the Olights, from respected reviewers. For the Fenix, I read that their measurements are known to be very accurate.

Ok, thank you. :+1: . Just be aware that method leaves a wide range of potential error for various reasons.

If you want to really narrow it down, do as Bob_McBob suggested above and get a set of calibration lights from maukka when you can. From my experience it makes all the difference in the world in getting more accurate measurements when I have a calibration light(s) with an exact known measurement to calibrate my tube with.

I found the lights maukka offers to be a great deal considering all the info he provides with each light. They are a ‘steal’ in fact.

Best of luck & thanks for sharing your project. :slight_smile:

Yes, tint will affect the results.

From this thread here

The Texas Ace Calibrated Lumens Tube was generally considered accurate to within 5%.

To maukka, what do you think is best diffuser for front? Do you have recommended diffuser films?