I’m getting ready to build one of these. Just curious what type of glass are y’all using and where are you getting it from? Thickness?
Got my glass from a local glass place. I’m using 1/4”(about 6mm) plate glass, 4.5” (114mm) in diameter. Cost me $4 + tax, and I had it in my hand 16 hours after I asked them to cut me the piece. I’ve got a piece the same size on order out of low iron glass when they get some in. Will be more expensive, but I’m not expecting it to be more than $6-8. Low iron glass is supposed to be more transparent (less green hue)
Some numbers from some lights I’ve measured. No solid (in my mind) calibration numbers yet, as I don’t have a good enough cross section of lights to feel comfortable with anything I’d call accurate, but .61 seems to be in the ballpark. (that’s the factor used to get the estimated lumens from the max lux in pipe values)
I’d love to get some feedback or suggestions on where it seems accurate, or way off base.
For reference, the conversion factor was 0.61, at max measured lux. I re-did the equations to reflect output at 30 seconds and they seem reasonable, but perhaps the factor needs to go up just slightly so the stock lights are closer to the average that other members have measured.
Edit: I take it back. It’s possible the number needs to come down a bit. Perhaps about 0.55 or so. That would put the dedomed ThruNite tn12 2014 at around 1000 lumens, which seems more reasonable.
Hello, I would like to make one of these contraptions but the only 4” 90 degree PVC elbow male on one side and female on the other so they would connect were $25 each. This can’t be a $100 project without the light meter. If somebody could post a list of materials and were they found them I think it would be very helpful.
Thanks
Michael
I just bought the stuff for this last week. Go to lowes or Home Depot. Don’t get the actual water line pvc, it’s the sewer waste drain pvc. Different section same aisle usually. Much cheaper. Like $4 for each elbow. I then took one of the elbows to the glass shop and they cut a piece of 1/8” glass to fit in it for $4. I bought some cheap $0.99 white spray paint for the inside and flat black spray paint for the outside. I hope to have it built Tuesday when I have some time off work.
edit for links:
4-in Dia 90-Degree PVC Sewer Drain Elbow
4-in Dia 90-Degree PVC Sewer Drain Street Elbow
I bought 1 hub-hub 90, 2 hub-street elbows, and a cap.
Consistency can have a few levels. If you mean to say that you get the same readings with same flashlights over time, or comparable readings to other people using the same set-up, or readings close to factory specs when flashlights with comparable beam shapes and colour temperature are measured, then the pipe, or a bathroom, is consistent and adequate (but the pipe is more convenient). I still can not see how a pipe can be accurate for vastly varying beamshapes, in other words: how good the integration is.
I notice some lights give the highest numbers when close to center, and others are closer to the edge on the side that would be considered the inside of the elbow of my pipe. Because of the inconsistencies measured when the lights where centered, and the consistency I could achieve finding the “hotspot”, I move the light to where it gives the highest measurement when measuring.
You can see one light in the chart that I posted a while back where I recorded a second run with a light, within 2% on 2 measurements made on 2 separate days. I’m good with the numbers my pipe gives me now. I’m using .55 as my multiplier to get an “approximate lumens” number and once I have some time with more lights whose ratings I trust and varying beam profiles I’ll be even closer to accurate data that I can tune the multiplier with.
KKW, did you do the T20’s zoomed in or out?
Flood mode, lumens doesn’t mean much to me zoomed in, for that I check candelas.
I just got through building mine. I gotta find a light for my correction factor. For stock lights, I currently have 3 UF-t20’s, maxtoch m24, small sun t08, hd2010, 2 jacob a60’s, and BLF x6. I did 1 of the t20’s 3 different times. The max I get as soon as I turn it on varies. After that they settle down around the same, but there is a pretty big and steady drop from on to 90 seconds (approx 200 lux). I didn’t realize they were that inefficient. I did my maxtoch m24 and it didn’t drop much at all which was impressive.
How much variance is acceptable at 30 seconds? 10 lux, 50 lux? How did you calculate the lumen, candelas, etc? Isn’t it better to use lux at 30 seconds
Variances happen for 4,372,833 reasons. If you control as many as you can, you’ll still end up with variation, and every now and then it’ll be more than you expect and you have to figure out why. Most of the lights I’ve double checked so far have varied far less than 5% in the pipe @ 30 seconds. I’ve gotten the occasional strange reading but always tracked it down to some error on my part when taking the measurement, or a bum tailswitch that’s causing fluctuations in the output. That’s consistency.
Now as far as accuracy, I’m still fine tuning.
Lumens conversion is based on some stock lights I’ve measured and what others have measured the same model.
Candelas is calculated based on:
(distance in feet to meter)² x .09290304 x (lux measurement)
For now worry about gathering and recording data and get a rough calibration factor, it should be easier to dial in your conversion to your satisfaction as time goes on.
Here is a list of results I have so far. No correction factor. The maxtoch seems pretty consistent. On his review, Mudgripz said this about the m24 “claimed is 82.5k for this light and mine measured peak 83.1k lux on meter at 6m”. So anybody want to help me figure out my correction factor?
^ Those look pretty consistent to me. Edit: consistent within the limits of the components creating the light to be measured, it’s probably not a coincidence that an higher priced light with good heat sinking gave you the most consistent results
You need to know the lumens your light should produce, divide the lumens by your lux measurement to get the multiplier to use for a correction factor.
Example: 200 lumen light that measures 1000 lux = 200/1000=.200
.200 is your correction multiplier in this hypothetical situation
Here are pictures of my setup. 3 long 90 degree 4” PVC elbows, a piece of 1/8” glass cut to fit, and a cap for one end. I used a strap tightened over the cap to hold Velcro in place which in turns holds the lux meter in place. I used black 1/8” foam cut to fit inside PVC with a hole to fit the flashlight head. I used just regular cushion foam over that to help hold the flashlight in place. Painted flat white inside and flat black outside. All mounted on a board with handles for easy carrying. Thanks to everybody for their ideas. There is a consistent difference in lux between the two meters. I like the LX1330B the best so I’m sticking with it. All my numbers are from that meter.
Well maxtoch rates the M24 at 1250 lumen. I’m assuming it is overrated. I guess I just need to make a thread asking if anybody has actual lumen output for that light.
On the X6 thread I found this:
well, I used the max lumen at 966, and 918 at 30 seconds. Using that for my conversion I get a cal factor of 0.44. Mine is a WW and not a NW, but it should be close. If anything my calculation factor needs to be a little lower, say around .4 to .42
listed as light - max lumen - lumen at 30s
t20 #1 - 686 - 619
t20 #2 - 673 - 627
t20 #3 - 686 - 618
Maxtoch M24 - 1036 - 980
BLF X6 - 959 - 906
Jacob A60 #1 - 304 - 249
Jacob A60 #2 - 309 - 264
The A60’s have a XR-E that is supposed to be 310 lumen so my measurements are almost dead on.
The M24 has a believable lumen number.
If I throw out my one set with the T20 #1 where it was getting really high numbers with the panasonic batteries, they are all about the same and pretty close to what you had for your stock T20.
what do you think?
you mentioned Candelas is calculated based on:
(distance in feet to meter)² x .09290304 x (lux measurement)
There is no way to extrapolate this data correct? I actually have to use my meter to calculate candelas at say 10m?
You have to make a lux measurement at a distance, the lux and distance go into that equation and it’ll spit out your number. There is no accurate way to extrapolate a candela measurement from the reading you get in the light pipe. Distance to the meter does not matter too much as long as you’re a couple meters away or more (for really big fixed reflector lights it may need to be 5 meters or more to be the most accurate), just make sure you measure the distance.
If my numbers are any good, and I think they’re pretty close, yours are in the same ballpark. Close enough for you to use the numbers. Just remember to list them as approximate lumens if you use the numbers here, I’ve taken to calling them “measured lumens in pipe” so no one gets the idea that I’ve got a fancy calibrated IS.
i hear ya. I may just drop my cal factor down to .42 to be on the safe side as I doubt my A60’s are running the specified lumens
My pipe looks almost just like that, it’s a dedicated PTrap though, not 3-90’s. Same meter. Manxbuggy1/rdrfronty built it for me, calibrated it with about 25 of their lights that were tested in their own pipe that was calibrated with over 40 lights. They bought quite a few high end lights like the Fenix and Nightcore and Eagle Tac that have ANSI rated outputs, those were heavily used to get their own pipe calibrated.
Mine has a conversion factor of .345. Tom E’s is also made by them and is (I think) .35 and even Richard uses one they made.
The absolute highest I’ve seen to date is my BTU Shocker with 3 XHP70’s and using (not recommended) 3 Panasonic PF cells. (I know, 12.6V into 3 6V emitters in parallel, scary for me, but I got a measurement) This was over 40,000 on the meter for some 16,000 out the front lumens!!!
I’m using 2 LG HE-2 cells in it, with the 3rd spot in the carrier having a 12Ga Turnigy wire soldered in, and getting 12,144 lumens out the front with a reading on the meter of 32,200 35,200. (Hope I’m remembering that right… I know it’s 12,144 but not 100% sure of the meter reading and am not at my own computer) This bad boy actually has about a 10 lumen moon mode as well. :bigsmile:
The lowest reading I’ve seen is using ToyKeeper’s firmware on a driver by Wight, the A17DD Hybrid-S with a single 7135 chip running the moon mode at 0.31 lumens.
So now y’all have me wondering…what if that sheet glass were replaced with a UCLp AR lens from flashlightlens.com? That regular glass simply cannot have the greatest light transmission and is almost assuredly costing us 10% or more right out of the gate. Maybe 10% isn’t much on a 600 lumen light, but what does that translate to on a 12,000 lumen light? 
Gonna get me some UCLp……
Edit: (went and double checked notes….the meter read 35,200)