Hello, I have just purchased all of the parts to build one of these light pipes except the light meter.
It seems that most people on here have the same light meter. Is that for any particular reason or because of cost?
If you were going to get a light meter for this light tube which would you pick in different price points? $10-25, $25-50, $50-75… etc. What benefits would I get out of a more expensive light meter? Are those benefits worth it?
Thanks guys,
Michael
Out of curiosity, is there a reason why everyone went with 2 sections of pipe? I am currently building a similar design, but I found 1 section still allows the head of the light to not have a line of sight of the sensor on my lux meter.
I think 4 x bends are better for proper light integration otherwise a thrower and flooder of the same lumen output wont read the same.
Because PVC is a bit shiny, I believe that the purpose is to limit the chance of a direct reflection. Based on some testing I just did, my light pipe with a sanded interior is nearly the same correction for floody lights and throwers(.52xlux for flood, .48xlux for throwers). Without the sanding the correction factors may have been further apart.
Actually, that reminds me. Anyone who has a light pipe who wants to be involved in the calibration thread djozz and I have started, you should make a post in this thread.
I’m interested in finding out what the difference in measurement corrections is between the sanded and unsanded interior on these PVC contraptions.
Thanks for the info guys. Looks like I need to do a bit more work on it then.
I had initially wanted to scrub the insides with acetone to dull the finish but never got around to it. The shininess does in fact contribute to a slight advantage for throwers. Just a bit busy now but do plan on modding my LMD in the future.
Hi,
I am recently interested in flashlights. One problem is that I don’t have any equipment to measure their outputs. This idea using PVC pipe/90 degree elbow sounds really attractive to me. However, since I don’t have anything to calibrate, is there anyway I can estimate the lumen from lux by some analytical or empirical formulas? As long as I can have a ball park number, I don’t mind some errors.
Another questions is what size of pipe/elbow should I use. Would 4” or 3” better than 1.5” or 2”?
Really appreciate your help. Thanks in advance.
Here’s what you do. Find a light with a known and verified ansi rating. I use a Fenix, but there are others out there. So if it’s 117 lumens…. you divide 117 lumens by the lux on your meter… it’ll give you something like this .25, .03, .59. Then you have your multiplier. Then when you put in an unknown light, whatever the lux is, multiply the .25 (or whatever) by the lux and you have your rating. Formula example- 117lumens/890lux= .1314 There are some problems though. Different styles of reflectors or optics can skew the ratings. So if you’d like to test many types of lights, it’s best to have a variety of styles of lights with known lumen figures. Like a big reflector thrower, a floody EDC, a bare emitter light- etc. The better measuring device you build, the more consistent your figures are.
I use 4 inch for mine. I’m using two 90 bends right now, but might go with a third. Some people have suggested sanding or find a method to make the interior less reflective. Painting the outside of the pipes black is also helpful. You need a lux meter, of course too. This model seems to be popular, mainly because it’s cheap.
I’m definitely not the expert- but I recently have built one.
mhanlen, thanks!
I looked the Fenix lights, they are ansi certified but didn’t see they are verified. May be you can get me a link to look?
I don’t know if there’s any way to get an idea about the mapping from lux to lumen without a calibrated light. It will be really helpful if someone can publish their “exact” setup and the test results, so if I follow them as close as I can, I will have some better idea about my lux readings.
The illusive ANSI lumen scale - no one really knows what it is, and sadly all the different manufacturers seem to have their own interpretation of it, and the differences are huge (IMHO). Here’s a good example, this independent reviewer has calibrated on “Fenix lumens” and shows nearly identical output/runtime graphs between a D25A and SC52 (I did the same test with the same result). ET specs 75lms x 2.5hrs, ZL specs 108lms x 3hrs, Selfbuilt finds the SC52 to be 120lms x 2.5hrs and on Fenix scale, they’re in the 94-98 lm range.
There’s only one reviewer I’ve seen that does claim ANSI accuracy (ti-force), with laboratory tested calibration lights, and his scale would put these graphs in the 84-88 lm range. This scale also happens match the high-quality US manufacturers like Surefire, HDS and Malkoff, so I think it’s right, but it’s pretty far off from the likes of Selfbuilt, ZL, AT, TN, etc.
In the end, just pick a calibration light and start working with it. As you collect and test more lights, you’ll change calibration lights and develop your own scale that matches most of your collection. Although I’m not fond of Selfbuilt’s liberal scale, his relative measurements are good so you’ll develop an adjustment factor to translate, and be able to compare different lights you don’t own.
The one thing I would highly suggest for calibration, is to use lower output modes, or step down outputs, and NOT max output. Max is highly dependent on battery quality, age, and state of charge, not to mention more volatile sample to sample, and generally have steeply sloping curves (so highly dependent upon the point captured).
Good luck.
I wonder how close the BLF A6’s will be to each other when they are in the 7135 only modes, there will soon be hundreds of them going out to members here.
reppans its funny that you mention ti-force. I was just getting ready to mention him myself in another thread. He is actually the guy that taught me how to measure lumens in the first place.
He did the original tests on my shorty maglite, and I have a light that I use that he tested years ago I have always kept for calibration of my own sphere.
They do provide 'some' output standard, but the leds alone will vary by up to 7 or 8%, switches cause varying resistance etc., but worse is that as I understand, Toykeeper's user interface does not contain a mode with just the 7135 on 100%.
What is the purpose of the glass?
It’s something to rest the light on.
O.K. Thanks.
Eventually, I went to homedepot bought some 4” elbows. I connect them together and did some quick test. The readings of throwers are quite consistent. I got 1400 to 2000 lux. However, for the zoomies, when they zoomed out, i.e., have a larger illumination area, their readings are similar (all are XM-L T6). However, when zooms in, i.e., has a small light spot, the reading is much lower. I noticed that it is probably because the reflections of the elbows are not very good. When zooms in, I can see a bright spot on the wall of elbow directly facing it. Do you guys observe the sam ething? Will paint wall black help? Any input would be greatly appreciated.
Zoomie zoomed in should be significantly less lumens then zoomed out, the lens is getting a much smaller amount of the LED’s light hitting it. How consistent is the lumen reading when you take a zoomed in light and move it around?