Warning long post ahead, bullet points at the top for those that do not care how the conclusion was arrived at
Howdy, DB custom was nice enough to donate his sphere to me to see if I could figure out the readings, So I guess I have a reason to post now.
Bullet points
- Got DB Customs sphere
- Tested every stock light I have
- Found massive variance between readings through-hole and through-wall and general unreliability of anything over 1000 lumens
- Also notice side issue of meter readings changing when set to 10x vs 100x
- Logged all the data to an excel file and crunched numbers
- Discovered that the light lost with strike bezels is the cause of most of the unreliability in through-wall measurements
- Discovered that heads larger then hole opening cannot be measured accurately.
- Spent hours testing materials for internal diffuser to increase the reading range of the meter beyond 1000 lumens with through hole measurement accuracy.
- Finally found that Styrofoam discs seems to work well and increases reading range to at least ~6000 lumens with much higher possible with denser/thicker foam.
- Found that a fixed multiplier seems to work great with internal diffuser and thus the sphere can be used like normal for any light that fits the opening. See pics later in post.
- Realized what time it was and fell into bed after a long days work.
Before I start I want to say that Josh did an amazing job on these. I am a bit obsessed with some things, one of those is ingenuity. I positively love the overall design of the setup, the way it is self-contained, it uses the shipping box to house everything, the design of the 3d printed parts ect. It is all top notch and very well thought out. Props to you Josh!
Only changes I think I will make to the overall setup is making some kind of shelves/holder for the rings and meter on the inside of the box, so I can move it around without everything sliding to the back. Well at least for now, I tend to add bells and whistles more and more over time lol.
I want to thank DB Custom for the sphere, I would not have been able to do this otherwise!
I also need to say that I have only skimmed this thread, what I am about to say may very well already be known, although I never saw my possible solution mentioned.
I got it in on Saturday and started playing with it yesterday. I spent all of yesterday working with it trying to figure it out and I think I might have figured out the issue and a solution to the through wall / over 1000 lumen light readings that everyone has been having.
So now to the testing. Sorry for the lack of pictures, I honestly got sucked into this saga before I knew or planned on doing it and didn’t think to take pics of anything, although not sure if they would be been worth it anyways, you have already seen the sphere.
I will post a link to the Excel document with the testing from yesterday for ya’ll to look over yourselves, it is rough as I did it in a long marathon binge of flashlights flying everywhere and telling people to stay away from the box because it is “important” and not “just a box”. The overall data in it should be understandable, keep in mind that batteries were drained some by the end of the say, so numbers that are consistently lower across the board could be due to that, ask if you have any questions.
The only stock lights I have that would work for this that I could think of at the time are as follows:
Nitenumen NE01
Defiant 3c 850 lumen
Convoy L6
Supfire M6
Astrolux S1
WELL USED and abused US serial number with OP reflector Fenix P2D, carried every single day for the last 10 years. More neutral tint then HK serial
Fenix P2D HK serial number and SMO reflector, colder tint and hardly used in the last 10 years
Fenix P3D
All the rest are modded or in various states of assembly.
Batteries are HE2 or HE4 that started at 4.15v or better, most ended up around 4v +/- a bit by the end of testing.
I then tested via the normal through-hole method first for all but the Fenix, which I remember near the end of testing. I logged the readings on each mode, along with any cases of the meter reading changing on another range setting.
I then repeated the testing with through-wall measurements. I didn’t have any meter issues with these interestingly
First I started out testing some small lights and it worked great, consistent and the numbers were in line with what I expected. Exactly how actuate they are? That is for someone else to figure out which multiplier to use, I have virtually no stock lights to calibrate it with lol. The .006 multiplier seems to work well though.
The issues started when I moved up to my more normal lights which are 1000+ lumens and over what you can measure through-hole. Readings suddenly were all over the place and anything but consistent or accurate.
After an hour or 2 of messing with things I decided to get scientific with it and run the numbers. So I pulled out every stock light I have and started taking measurements. Logged everything and then studied the data.
About halfway through testing I figured out half the issue, which is that lights with “strike bezels” that let light escape from the front are impossible to calibrate no matter how you take the readings. There is simply too much variance over the output levels in light lost. The more light that escapes the worse it is to try to get an accurate reading. These became very clear when testing a SRK (not in the excel file) with 8x XM-L2 U2’s. The higher the mode, the further off the reading.
On the other hand lights with smooth fronts (such as the S1) read spot on with the through wall measurements. So this was the first major issue.
The next issue was for lights that are too big to fit in the hole, put simply, it is impossible to get a reading on these lights, it simply cannot happen. For example an L6 reads ~2500 lumens with a through wall measurement even though it is actually around 3500 lumens. This is due to the fact that the multiplier for the through wall measurement is skewed due to a lot of light being lost when taking the through hole reference. ~29% of the light is being lost to the edge of the foam.
This is impossible to account for, so unless someone has an idea on how to get all the light from a large head into the sphere and take a reading, a flashlight with a larger head then the through hole cannot be measured sadly.
Lastly the other issue that I have is that the lux meter disagrees with itself in certain ranges. For example on some lights I will get one reading in the 10x range but a completely different reading in the 100x range. I have no idea why this happens but it happened with my other lux meter as well. It only happens a few times but when it does, neither reading seems to be “accurate”.
It is repeatable, with the same light on the same setting. No earthly idea why this happens at all but it plays havoc on the averages and needs to be eliminated from the numbers in order to get an accurate multiplier IMHO. The only thing I can possibly think of is maybe the PWM of the light is somehow causing the meter to spaz? doesn’t make much sense though since it does it with my meter as well.
Once I knew these issues I then set about figuring out a way around them. We are always smarter than the problem, thats my motto and I want to know what my lights are making!
After a lot of thinking, testing and playing around I finally hit on something that seems to work quite well.
Basically the through hole measurements are great, they are reliable and besides the exact multiplier, they are accurate. The issue is measuring lights over ~1000 lumens which maxes out the meter.
The idea was to do a thorough wall measurement in order to diffuse the light enough that the meter won’t be overloaded. Great idea, one I experimented with on my own earlier this year with a PVC sphere (where I ran into the same issues, although since none of the readings were known accurate it was impossible to diagnose it). In practice though this simply does not work with most lights since they have strike bezels.
So we needed to eliminate the through wall measurements and yet still diffuse the light, so why not make it that simple? Lets simply diffuse the light inside the sphere.
I tried a bunch of things from white plastic lids to bowls ect but most of them did not diffuse the light enough to get a worthwhile increase in the measurement range to be worth it.
I then figured that if the Styrofoam wall was enough to diffuse it, why not use more Styrofoam inside the sphere?
I then found some 5” x 1.5” Styrofoam discs (well 2x .75” discs stacked) and I put that over the sensor inside the sphere. Being a circle it seals up nicely just laying it there but mounting it would indeed improve things.
Pictures of the internal diffuser:
With this internal diffuser in place I then took all the readings again. Did them just like the through-hole measurements.
All the sudden the readings on the powerful lights started lining up perfectly with the “open-hole” readings.
After taking all the new measurements and averaging the numbers, this particular diffuser setup (could easily be changed to allow for more or less lumens), a multiplier of .037 seemed to work across the board. Virtually all of the readings taken with the diffuser and using that multiplier came out to spot on what I would expect across the range (aka, the modes were spaced as they should be, if not exact on the lumen number). They also match up almost exactly with the non-diffused through-hole readings.
Every light I tried came out perfect and honestly the sphere is a lot easier to use like this since you would not have to change the test process no matter what the light output.
I am curious to hear what people’s opinions on here are about it. I welcome you to try it yourself and report back.
I have not mounted these discs yet as since these spheres were designed to be standardized I wanted to see if we could come up with a standardized way of doing this before customizing this one. Plus ideas on how to mount it while still allowing it to be removed if desired are welcomed.
Here is the excel file with all the raw data
Josh’s Standard Sphere tests Raw data
I welcome any and all comments.