CNC,
Good to see you chime in with links to your experiments. I missed them first time around.
Sometimes these things are of great interest, but for whatever reason never get any notice.
I tried paints on the outside and inside of the elbows and none came out ahead of the bare elbow covered with foil as far as transmitting max Lumens.
I didn’t try any of the exotics like barium sulphate powder mixed with a binder.
All the Best,
Jeff
Try this (all without moving the lights)
If A + B is the same as the measurement for them both combined then you have evidence that your device is linear.
I tested my sphere like this and IIRC it was much less than 1% different.
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Hmmm… I don’t have a Q8 to test, sorry. Once was looking for a Q8 driver to put in a build but could not mod it for a 90.2 led.
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Yes, ” the higher lumen lights did not come close to the expected results ” exactly as you asked. I used “maukka” calibration lights at first and I could get good results attaining a multiplier number within 10% of 1.0 only on lights with less than 2000 lumens that were not strong throwers.
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So I tried to calibrate them with a ( stock ) “HaikeLite MT07S - HI CREE XHP35 HI LED 2700 lumen” and a “Manker U21 1560 Lumen Pocket Thrower CREE XHP35 HI LED”, both mid size throwers.
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This seemed to work with “.960 multiplier” for the HaikeLite MT09R ( flooder ) at 24000 lumens, 29.8 amps 6 volts.
The modded water cooled “Matenminco MT35 PLUS XHP 70.2, 7.8 amps 12 volts” ( thrower ) at 9000 lumens.
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At this point it seemed fixed or close enough until I finished the next 2 mods with the 90.2 led and the readings were too high again, which also left previous readings in question. I gave up at this point.
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I am not convinced a lumen tube will function for every type of light.
They seem to favor FLOODERS for more accurate readings.
More experimentation will be required to solve this problem, hopefully we can be successful. 
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Sorry, I keep editing this post.
All my lumen numbers for all my posts are approximate, not accurate.
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I thought it was you who had modded a Q8 w/ 4 x XHP50.2s and had like over 10k lm. My bad then.
So once re-calibrated for the monster throwers, the numbers don’t work with the SBT90.2. Granted, the Luminus is ~5600 to 6000 lm. Not the same ballpark as the 9k and 24k beasts.
Did some testing on my own with some DC Fix filter between the light and the entrance point to my box. Tested SST70, CSLPM1.tg & CULPM1.tg and the results altered by some 10 to 25 %. But nowhere close to Djozz data or Osram’s spec sheets.
Hotspot isn’t too pronounced when I look at a white wall with the filter. But I could leave it as such, being just 3 lights are erroneous. I’ll have to check the FT03S w/ the 90.2 – but that needs some setting up as I had some ‘yoyo’ effect with the driver and did make a few mods.
As Djozz has extensively tested LEDs and per his observation, the lumens correlate to the lux meter’s. His set-up is using an integrating sphere, so the spherical aspect would be the proper integration method?
Edit: addendum…
Exchanging with Jeff (PM), he suggested I add an elbow to the lightbox, to better distribute the beam evenly. Might try that. And then again, your setup is tubular and the results don’t concur.
If I had seen a good difference in my diffusing trick, I might have given some thought to transporting the lumen “box” to a honeycombed aluminized food delivery cardboard box. But I have to devise some support system as these boxes aren’t too strong. Just repeated opening and closing tears the aluminium. Don’t like using plywood to enclose the thing, becomes too heavy for quick use.
The reason for the straight 8” tube was for a large surface to have light dispersed on it by a diffuser in front of it. But the tight beam from the 90.2 was still too condensed in front of the light meter and penetrated it, giving a higher reading. If more diffusion is added then the 70.2 is low. I already tried this. Thinking after some time and a fresh look maybe some idea will emerge to get both led to use the same multiplier. Without a calibration light for both led, I’m not sure it is possible. This may be easier with a giant lumen Intergrating sphere, lol.
Just now working the details of wrapping my aluminized box with coroplast. Lightweight and a bit of arts & crafts to make. Transporting the white PVC fittings, maybe get better results.
Would you make the apertures as far apart? on the cover.
Addendum:
Would placing your light meter within the 8” tube, say some 4” from the bottom and facing down. Somewhat like a reflecting telescope. The light beam would have to bounce from the bottom surface to be registered.
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I don’t understand what your saying ” Would you make the apertures as far apart? on the cover. ” Are you putting holes in for different size lights ? If so, then no, use rings to block any light around the light and install only one hole big enough to accommodate your biggest light. Reason is positional consistency and relationship of light coming in and the light meter.
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You are correct about the position of the light meter in the 8” tube, it is wrong. The tube is linear and I was trying it anyway, LOL. Before it gets relocated, I wanted to try installing a cone shaped diffuser to see if it improves any.
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I am no expert on lumen tubes, just a newbie shooting in the dark.
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Right, didn’t post my little styrobox setup (that was in PM w/ Jeff, things escape me).
And testing a bare LED with fan-cooled aluminium heatsink:
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The reflectiveness of the white styro screws up the white balance – hence the darkness of the pics.
I’m using a series of black rubber gaskets to adapt to the various sized lights. My original idea of using a diaphragm (shutter) is dismissed. This had some problems of its own, I think the lens is composed of two laminates and throws off the beam’s linearity. The aperture for the lux meter is an aluminized 90º cone terminating in a soft polyethylene ring that just fits the meter’s aspheric diffuser (hardly seen, but the blue ring on the right).
And so my question was best to distance the two holes (one for the emitter input, the other for the lux meter) as far apart on the new aluminized box? This one I balanced the apertures as the box inner dims are rather small.
I came to the same insight about a cone to diffuse the beam, placed in the bottom of my box. Found this little paperweight and gave it a coat of white paint.
As for your 8” light tube, without any schematic, I’ll elaborate on an idea – although you can conjure up a better design.
Making a cone (provisional white cardboard) and gluing some shish kebab sticks or some TIG weld rod or anything somewhat that props the cone from the bottom, passing one of your cabled lux meter sensors to the underside of the cone, tying the cable to one of the legs and thru the bottom opening, which then gets closed with some reflective material.
^ – seems lame for a mechanically oriented machinist, but simplicity sometimes makes the cut – ^
Just a cut and try setup. If the results are positive, make a better sheet steel cone and with some welding or mechanical fixations.
Addendum; I would like to have my small styrobox working as it’s just small enough to place on my off self in my little shop. Using a larger box would require me to set it up in the basement, not so convenient as at arms reach.
Same goes for a tube set-up or a spherical one.
Ok, ran some tests w/ cone:
SST70 : ~2900 lm, was ~2700 lm, Djozz ~3500 lm
Hence a slight increase in lumen capture but not up to specs.
Without the elaborate coroplast wrap to my aluminized box, I’ll make a makeshift rig and test further.
Addendum:
Makeshift set-up with the aluminized lightbox
SST70 : ~2700 lm
Results aren’t as expected (deceiving). Same as with the styrobox w/out the cone (but w/ Boaz filter #13).
Will have to give some more thought…
Sidney,
As far a gaskets/bafflels to adapt for different light head size. The inside face of the gasket needs to be lined with foil (or reflective something?) or it will soak up those pesky photons. As the gasket changes size, it throws the reading (in my experiments) off to a greater or lessor degree (if not lined with foil).
The black anodizing from the light should be covered as best as possible also.
This bike light with the oval reflector. The light measures.
With Brown cardboard baffle matching the outside diameter of light: 365Lm
With Foil covered baffle matching outside diameter of light: 437Lm
With Foil baffle and added bits of foil to cover everything except the oval reflector: 452Lm
All the Best,
Jeff
I’ve been researching candidates for a reference light. The Photo world has some possibilities.
Some questions for you, brighter than me, souls.
It seems that the photo world suffers from the same sort of shenanigans that the flashlight world does as far as specs.
The light specs are usually listed in lux at a certain distance. At 1 meter or 3’ depending on maker.
Often with a beam angle included. Getting to Lumens is easy since the area can be calculated.
But it is obvious that some manufacturers are playing tricks to come up with numbers that don’t make sense. For example a 100w light from one maker calculates out to something like 70,000Lm given a 160 degree spread. While another 100w light claiming a 60 degree spread calcs out to maybe 18K lumens. (These are just made up numbers to use as example)
So, give me some guidelines. Since watts is watts, about how many Lumens can be reasonably produced by a COB LED at:
60w, 100w, 150w, 200w ?
That will help give me something to compare reality to fiction.
Thanks,
All the Best,
Jeff
On the subject of baffles;
Thanks, I’ll take note of that. I didn’t elaborate on the details, but with different light sizes I use a rubber retainer (large ‘O’ ring) but I fill with these plastic rings (white) or some stainless ‘rings’. It was my intuition but I’m glad someone went thru the trouble of checking the variations.
I’ve come to some enlightenment (pun intended).
1- the larger aluminized box doesn’t disperse the light evenly and the results are not any better than my small styrobox.
2- more voluminous (5½ internal, 1½ external times more than the stryo), it takes up much room and is very fragile.
3- using a cone in the bottom of the box does help with the hotspot deflecting.
4- with better filters, I may be able to diffuse the beam more thoroughly and that seems to be your endeavour also.
I looked at some of your posting on your build. There’s much there so I’ll take it some step at a time. I’ll have to verify against some other throwers as the Osrams ’cause the SST70 may be at fault (the 1st driver failed, the second I butchered and this third one, albeit Convoy’s, may need some checking of the claimed outputs).
On reference light;
Not meaning to throw your query in the air, but the efficiency of these COBs is getting better with each new generation. I wouldn’t think of placing a lumen value to a given wattage.
Did you not see my post (PM) of the StratusLed? Did take some time to dig that out (~2 hours). I thought it would be a good candidate.
At this point, with my little dilemma, I don’t see/understand why a higher lumen reference light for our lumen contraptions. As Djozz has pointed out, the lux value is proportional to the lumens, regardless of the type of illumination. That is to say, the meter should respond linearly to the light flux. It would seem the dispersion of the hotspot is the key to even out the beam. Djozz doesn’t have this problem, and he’s been collecting data for eons. His set-up uses a sphere, so I would argue the shape of the integrator is key.
I’m no specialist, just a tinkerer.
That’s a clever way.
However, our little dilemma is rather the hotspot of throwers is not registering as additional lux.
Lux is the perceived illumination level whereas lumens is the total amount of light given. So the hotspot of the throwers is intense, what we would perceive as luminous, but our meters do not compare the said spot to the spill, it averages out the total illumination and doing so lowers the net value.
So myself, Jeff, and CNCman are trying to even out the light beam, so the meter can average a better sample size.
SS, I did miss your PM. Thanks for the info.
dave, this is clever way. My Tube isn’t big enough to put a pair of real boomers in there. But I’ll give it a test with some smaller lights.
I do think the lux meters are linear (until proven otherwise). Though the cheap ones I tested do show different lux readings for the same light source and that needs to be dealt with in the Lumen conversions. Think I remember T_A saying he had to do so in his Tubes.
It’s our Tubes/Spheres/Boxes I’m suspicious about.
The margin for error on a 250Lm light vs 25KLm light.
All the Best,
Jeff
Closure to my hotpot dilemma:
After some analysis and further number crunching, I came to attribute a different value to my reference light. This is not a Maukka light but my evaluation of a constant output single-mode light.
I kept the cone and single diffuser film (Boaz #13). My results:
SST70 : 3525, was 2700, Djozz ~3500
SST40 : 1140, was 880, Djozz 1400 (5000ºK vs. 6500ºK)
Osram HX :1480, was 1020, 1700-1900 (OEM’s specs.)
Better values but still short on some lights.
In conclusion, this will have to do. My lumen values will be with some caveats as imperfect, but in my builds, they will suffice as a comparison.