Lumens measuring contraption (feedback please!)

turboBB

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Wanted to throw this idea out to the experts, so please humor me if you will...

Two things lacking from my reviews have been:
- PWM readings (building audio cable connected to solar cell and will use a PC soundcard oscilloscope program)
- Lumens measurement. While I can do a ceiling bounce, there are usually too many factors introduced (beam shape/intensity chief amongst them)

For the latter, I've been meaning to build an IS but don't like the idea that there would not be a stable platform/holder for the light while I'm taking measurements (especially for runtime logging). Also, based upon what I've read, I felt tweaking the baffle has been one of the trickiest parts to calibrating it properly. So I came up with this idea based on the following criteria:
- must accomodate bezel head up to 4" in diam
- allow consistent repeatable measurements
- provide stable platform for light to rest on while doing runtime / logging and light must be exposed to allow fan to cool it
- not be affected by ambient lighting while logging is in progress
- no fiddling w/a baffle
- simple to build w/easily sourced parts
- reasonably budget friendly
- allow light sensor to be easily removed for other measurements
- easy for others to build/reproduce

I've read about a PVC U-pipe idea but decided to add an extra 90deg. elbow to further reduce the likelihood of any direct reflection making it to the light sensor and ended up with this:


Total parts used cost $34.40 before taxes:
- 3 x 4" 90deg. PVC elbows
- 1 x 4" -> 3" step down adapter
- 1 x 3" -> 1.5" stepd down adapter/cap

The entire contraption will be strapped/bolted onto a wood base. The end where I'm shining the light into will have a glass/plastic lens over it that can accomodate lights up to 4" and establish a platform for the light to rest bezel down on and be completely exposed to allow a fan to keep it cool. I'll cut card board/paper templates for smaller lights that will allow perfect centering thus allowing consistent repeatable measurements. The other end w/the step down adapters will need to be sanded down to fit but will hold the light sensor.

Worst case is that if this doesn't work, since no glue or alteration is involved, I can return the 3 x 90deg. elbow which was the majority of the cost for this project. The step down adapters will need to be sanded down and can not be returned but I'm sure I cand find other uses for them.

For now, just as a POC for myself, I skipped the step down adapters and just placed the sensor at the lip of one end. I placed a piece of glass on the light end to hold the light in place. I noticed that I'm allowed some flexibility w/the placement of the light w/out affecting the reading drastically (the sensor however will read a bit higher once centered in the step down adapter).

Here are some lights with the mfg's claimed ANSI values and what I measured (PVC) after 30 seconds:

Icon Link

High 50
PVC - 41

Klarus XT20

High 1200
PVC - 1222 (this light uses PWM even on high so I actually should've done an avg instead of eyeballing a single value)

Niteye EYE30


Turbo 2000 / High 1000
PVC - 2117 / 1100

SureFire M3LT

High 400 / Low 70
PVC - 669 / 139.5

SureFire E2DL

High - 200
PVC - 234

Sunwayman T20C (forgot to take pic)
High - 438
PVC - 290

Sunwayman T40CS

High - 788
PVC - 745

Sunwayman V60C

Max - 728
PVC - 831

Xeno G10v2

High - 460 OTF
PVC - 440

So it seems like it's not too far off and thus far doesn't seem to be favoring throwers. There are of course a few anomalies like the V60C. I know for sure lux was lower than the T40CS thus why I'm surprised why the lumens measured this way was higher.

Of course there's consideration to be given to the semi-glossy surface of the PVC so I may look to coat it w/IS paint. Anyways more experimenting to come but what are your thoughts on this?

I am by no means an expert on this and can use whatever guidance and tips you guys can provide. Also, the above readings were pure lux w/no conversion done.

Cheers,
Tim
 
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Flying Turtle

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Nice work, Tim. I look forward to seeing how this progresses. i wondered about the shininess of the PVC, too. Has anyone ever tried painting the PVC black? Maybe that wouldn't work at all.

Good luck,

Geoff
 

selfbuilt

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Interesting setup Tim, curious to see where this goes. :popcorn:

Can you fit a smaller adapter at the end that goes to your lightmeter? I notice a lot of light escapes the opening, so the effect of the internal reflections could be variable for different types of lights. Would probably be better if you could get that down to a much smaller opening.

I am surprised at how well my milk carton lightbox (which has a matte internal finish) works to sum up the light. But in my case, very little light light escapes, except what isn't caught by my back-drape around the light bezel opening (i.e. my sensor is permanently embedded, in a perfectly cut hole).

I remember when Doug tried painting his milk carton, it didn't make a difference (since already pretty matte). It may have more of an effect here, given how shiny white PCV is. I wonder how black PVC would do? You could probably find a lot of connectors in the plumbing section of your local big box hardware store, if you wanted to give it a go. But white is probably best, as long at it isn't too shiny.

By the way, is there any way to lower the sensitivty/increase sampling time of your lightmeter so the PWM isn't a confounding factor?
 
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turboBB

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Thx guys.

@selfbuilt - yes, that's what the step down adapters will be for, I just decided to do a test run w/out them for now since I don't have time to sand them. I wanted to go the milk carton route as well for the ease of setup but the only prob is as mentioned, I wanted a device that I could actually rest the light firmly on to conduct runtime testing as well as accomodate 4" bezel.

Until I get the IS paint, I'm going to start scrubbing the inside of the PVC w/0000 steel wool and acetone to dull the finish.

As for my light meter (Extech HD450), unfortunately there's no way to set the sensitivity (as a FYI , I had it set in the 4K range) but as mentioned, I can do an average so as to reduce the fluctuations in the future.

I've got a bit more work to do on this thing before I can even start claiming that the numbers make sense. For now I just wanted to pitch the idea out there to see if it was just totally off the walls but based on various feedback, it does seem like it could work.

Cheers,
Tim
 

flashflood

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As for my light meter (Extech HD450), unfortunately there's no way to set the sensitivity (as a FYI , I had it set in the 4K range) but as mentioned, I can do an average so as to reduce the fluctuations in the future.

Could you work around this by using phosphorescent paint? It would effectively act like a photon capacitor, i.e. a low-pass filter.
 

turboBB

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I'll eventually tackle the PWM issue but for now my main concern is whether this might even work and thus far here's the deal, I was afraid that this might favor throwers, and perhaps it does to a very light degree and as much as I remain a little skeptical myself, the readings keep telling me that I just might be on to something.

I took a few more measurements of most of my lights and they are all within % of claimed ANSI or mfg claims (and again using the same set up as above as I didn't have time to sand and paint yet).

I think these two test subjects are the clearest example that this might work:
This is the eGear Focus Control headlamp, it can be focused from flood (left pic) to spot (right pic) and in spot mode, it only increased the reading marginally:


This is a LumaPower XR-E R2 w/TurboForce Kit that casts a pencil beam sized hot spot (check my beamshots threads in my sig for beam profile) and if this contraption did favor throwers heavily, then this reading should be much higher but I think it's fairly relative for a XR-E reading:

L: Lux reading | M: stepped down to show beam profile | R: diffused light at other end

I don't have time right now to post the rest of the pics but the full album is here in case you want to take a look. I tried to include most of the light in the pic so you can identify them (EDIT: forgive the bag in the pic, it's acting as a ballast to hold down the pipe).

I'm sure the readings will be different once I sand down and mount the sensor in the center of the pipe but at least this seems encouraging no? More to come!

Cheers,
Tim
 
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TEEJ

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Tim,

Does your meter have a peak capture on it?

The one I use for work can be set to record the highest (and lowest) recorded readings. Essentially, I press a button that then samples for a couple of seconds, and saves the highest and/or lowest readings.

The highest reading would allow you to grab the pulse peaks at least.

If the PVC is channeling the throw from the lights, and you want to account for that, I'm not sure if black is best per se.


Your estimated lumens seemed generally low, potentially due to the end with the light not being part of the box, and some light going the wrong way, etc.

This can also favor throwers, as less of the thrown light would reflect back out towards the flashlight hole.

The spheres I've seen are white inside, which makes me think white might be better than flat black for example.

Being shiny means more of the total light that's emitted might make it to the sensor. Given that the purpose to to gather every lumen and turn it into lux at the sensor, the more reflective the capture mechanism, the better it should be at that.

I think that's also why the use a sphere in the first place...to have the reflections even out/homogenize, etc.

Otherwise, all you'd need is a sensor the same size or larger relative to the light source being emitted...attach the head of the light to the sensor, and the entire beam would shine upon the sensor for direct measurement.

Short of that, the devices are essentially trying to simulate that concept...try to get the sensor to sample all the light, or to homogenize the intensity of the light with a sphere so that the sensor can sample a representative portion of it, and the rest be extrapolated, etc.


By making the light have to take a torturous reflector path, it will tend to have the throwier part reflect differently than the corona or spill, etc. This leaves it less homogenized, so that what you measure is less representative. A duller surface might exacerbate that issue. Of course, the slight changes in angle, depth and rear reflectivity when the light isn't mounted as you intended for the permanent solution, would also add to the variables.

Off the top of my head, shining the light onto a concave reflector to take the entire beam and compress it, and then perhaps measure either the output if it worked out to a convenient size, and/or shine it through a lens to make it "sensor sized".....onto the sensor, might allow collection of more of the light emitted?

Going the other way to homogenize the light emitted, you could shine the light directly at a mirror that was faceted to break up the hot spot, etc, or convex, etc...and reflect the homogenized light back towards a sensor?

IE: the Light could shine north at the convex mirror inside the reflective chamber, and back south towards the sensor.

Just thinking out loud...:party:
 

turboBB

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Thx TEEJ, this was really more of an experiment to satisfy my own curiosity than anything. I do eventually still plan on building an DIY IS but wanted to see how this would work out. If nothing else, it would make an excellent platform for runtime testing (plus I have a design for this to act as a decor in my kids room). I likely won't be able to make any progress on this until the weekend but will be providing updates here whenever I do.

I also need to send out a few of my lights for testing on a real calibrated IS before I'll even begin to know how to make sense of the readings from this thing.

Cheers,
Tim
 

TEEJ

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You asked for feedback...so I was trying to provide some. :naughty:

If you want to borrow my light meter let me know, I'm not scheduled to use it for anything in the near future.

Also - If sending stuff out for IS measurements, if you think it will help, let me know if you could use any other lights for comparison, like the De-domed SR90 or DEFT edc LR, for throw, or a different tint Big Bruiser or a RRT-3 XML, for flood, etc.

:D
 
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turboBB

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Thx a lot TEEJ! and I apologize if I came across as brushing aside your ideas, it was not my intention. I just realized that in order to start making sense of the readings, I need to have solid accurate data first, otherwise it'll just be guesses.

I sanded down the step down adapter yesterday but by having that in place, it reduced the reading tremendously... this reinforces the fact that I need to establish a baseline first before I can start applying any corrective values etc.

Really appreciate the offer to borrow some lights and will certainly take you up on it. Hopefully I can find somewhere local to get them tested (will let you know). Maybe someone w/one might be kind enough to bring it to PF18. ;o)

Thx again!,
Tim
 

TEEJ

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Thx a lot TEEJ! and I apologize if I came across as brushing aside your ideas, it was not my intention. I just realized that in order to start making sense of the readings, I need to have solid accurate data first, otherwise it'll just be guesses.

I sanded down the step down adapter yesterday but by having that in place, it reduced the reading tremendously... this reinforces the fact that I need to establish a baseline first before I can start applying any corrective values etc.

Really appreciate the offer to borrow some lights and will certainly take you up on it. Hopefully I can find somewhere local to get them tested (will let you know). Maybe someone w/one might be kind enough to bring it to PF18. ;o)

Thx again!,
Tim

That would be cool of them....does someone around here HAVE one?
 

jasonck08

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Very interesting project. I'd be curious to see how the readings would compare if you take a reading with the reflector on a specific light, then remove the reflector and lens completely. The reading should be higher without the glass lens and reflector, but my guess is that the reading would be lower...
 

turboBB

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I actually did that w/a T40CS and the output measured w/out reflector and lens was drastically lower. But I suspect it would be the same w/a real IS since the light is simply not being directed forward (in my case into the PVC and w/an IS into the sphere).

This has been good for comparitive purposes but I'm on the hunt for a sphere now... ;o)

Once I have that up and running then I can revisit this to challenge the readings and see if I can actually tweak this device to make it meaningful.

Thx a lot for the feedback everyone!
 

turboBB

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OK, so I actually haven't done any further fiddling with it and literally been using it as is w/out the adapter. Where it deviates from my original requirements is that it will be affected by ambient lighting so I need to take measurements in a pitch black room. While I don't have a baffle to deal with, thx to feedback from a member, I found out that ambient temp will affect the readings. So each time before I take readings, I'll first use a Xeno G10v2 (as Xeno uses ANSI values and it immediately runs nearly perfectly regulated on medium) to calibrate the sensor's positon to match as close to 158lms as possible. Then I'll check the other levels to see if they're close to 480 and 10 on High and Low respectively.

The PVC (lms) column is what I've measured for each light. The output is measured in lux but wouldn't be far-fetched to call it lumens as the readings are pretty close for most of the lights. As expected in SureFire's case, they are known for underestimating their lumens and my readings corroborate that. Judging by the measurements, Sunwayman is also a little on the conservative side as well. All my measurements are done at 31seconds after turn on but of course it's not known at what time the manufacturers take their readings since it can be done anytime between 30secs - 2min.


As you'll see, it doesn't necessarily favor throwers. Case in point, the T40CS is near~47K lux and the V60C @ ~36K lux but yet the V60C registers 904 lux (lms) vs. 814 for the T40CS.

While I wish there was some engineering formula I could provide to calculate what is happening to the output after three pipe bends to produce these results but in a way it's been great not having to. I'm now able to consistently reproduce comparitive WISIWIG (What I See Is What I Get) figures of how one light is faring vs. another.

The real nice surprise aside from the Sunwayman V60C were the ThruNite TN 10 & 11 as those readings were taken on only 1 x 18650 each, I'll post 2 x 18650 config (including step down) when I get around to them.

Anyways this has been a fun expirement for me and useful for comparitive purposes. Anyone else care to give this a spin? Assembly takes all of 5 seconds after you get the 3 x 90 deg. elbows. ;)
 

turboBB

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THIS is one of the reasons why one of my requirements included being able to accomodate 4" bezels (sorry for the horribly blue tint, forgot to set camera to AWB):
14e7583.jpg
 

Solscud007

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Yes Tim, great job indeed. I got to see this thing firsthand at PF18. Im glad I didnt leave as I intended.

We tested my Hellfighter and it is putting out 5,000 lumens!!!

p1010110.jpg
 

turboBB

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Thx for posting solscud! That really was an amazing piece that Mac crafted for you (one more pic of your light down below).

All,

I took a few shots at PF18. We tested lights ranging from .3lms up to nearly 9K. Thx to the 4" opening, we were able to measure all lights although we had to remove the glass lens for ma_sha1's short arc though ;)

We were also able to demonstrate again that this doesn't really favor throwers since a TEEJ'S DEFT aspheric came in only around 80lms, otherwise it should've thrown the reading well off the charts. Too ba we didn't have a known calibrated light although an HDS Rotatry came in at 122lms these are known to have nearly perfectl flat regulation.

Without further ado, here are the lights we took and since I can't remember all the details, for those that attended PF18, please feel free to pipe in and identify/correct any lights below.

A few of Mac's Customs:


Mac's Eagletac?:


ma_sha1's short arc (can't remember the final ouput):


solscud007's Hellfighter w/custom battery tube by Mac (I think this was originally over 7K and quickly dropped to roughly 5K+)
7f4321e.jpg


Sorry, I can't recall whose light this was but it was around 9K on weak batteries after the quarry run:


Same here, don't recall whose light this is:


Anyways, PF18 was a blast and if any of you do actually put one of these together, I'd love to hear your feedback!

Cheers,
Tim
 

TEEJ

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IIRC, the Deft edc LR+ was 80 lumens,

the DRY 3 XML was 3,300 lumens,

the Fenix TK70 was 2,650 lumens,

the De-Domed Olight SR90 was at 1,350 lumens (About the same as the 1,400 lumens Selfbuilt measured for the Domed version),

the 4Sevens S12 Copper was 1,000 lumens,

the 20 watt Stanley HID (HIDC10) was 1,300 lumens (But rated at over 2,900 lumens..a bit optimistic),

the Nitecore TM11 came in at its 2k lumen rating,

The Klarus XT11 was at 850 lumens after the drop (On 2 RCR123A's), didn't measure before, it was in use outside already...,

of mine checked, that's all I remember right now. (Well, that I at least remembered to write down that night when you measured them...)
 

ma_sha1

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ma_sha1's short arc (can't remember the final ouput):

This is the Mega Blaster with 120W UHP lamp & a big Aspheric head, it read just over 7000 lumens.
(7500 lumes when I dip the head in the tube a bit, didn't rest the head on the glass as I was afraid of bliding people by reflection).

I also read my key chain 10280 Li-ion XPE light, it read 110 lumens. I think I had pretty close to two ends of the range, I had to say it worked pretty well. The UHP short arc lamp spec is 60-65 lm/watt. Which translate to 7200-7800 lumens range. Looks like I didn't lose much, most of the light managed to get focused & came out the front, I am pretty happy about that.

I also agree that it doesn't seem to favor throwers, it it does, the readings would have been way out of wack, as the Mega Blaster has a measured candle power of 5 million lux @ 1 meter.

Mega Blaster in action at Black hole/PF18. (Photo taken by CPFer WadeP)
(16 million cp Moon blaster to the left & BVH 85Watt Blits spot to the right)
scaled.php
 
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