Great input Texlite, the more expertise, the better! I’d love to see your powerpoints about the subject. Direct posting is nice, but if it is too much work, you could drop them somewhere and post a link?
Found the place I bought my styro sphere from, it is indeed 16”, and miraculously, I was also in the ballpark for price~$38. The bad news is they’re no longer on the site, the link is dead. I’ll post the link as it has the model number, maybe someone can dig up another source. Barring that, they can be made relatively easily out of a cheap bouncy-ball and fiberglass or papier-mâché.
Here’s the link: http://www.smoothfoam.com/mm5/merchant.mvc?Screen=PROD&Store_Code=PCO&Product_Code=10073
-Michael
Great stuff happening! 
I’m a little worried about through wall, but won’t use it for my bigger lights if it proves problematic. I DO have lights that will melt the styrofoam, in short order. Even the 5000 lumen M6 is capable of that.
I have a UCLp floor plate on the way for my PVC Trap box, courtesy of Chris (Thank You Chris! ) so I’ll report on my findings on how that impacts the readings.
That is a very nice powerpoint about the problems you encounter when a luxmeter is used for led lighting! Thanks for sharing, I can recommend everyone to read it.
Our biggest problem right now is a source of rated lights to perform the calibration with. I PM’d manxbuggy1 and rdrfronty yesterday, no word there yet.
I received a Lux meter today and did learn my BLF A6 is ultra sensitive to battery charge, so getting some constant-current lights here for calibration is an absolute must.
I just got in a 1330B, my 2nd, and after doing a few experiments of room light and PVC pipe light box of various lumens levels, I’ve found the new 1330B reads 4.35% lower than my old meter. The new meter was bought off of eBay for$20 shipped - from the eBay user ivandogone mentioned earlier in the thread.
I emailed him about the issue and questioned about his sourcing, but of course he did not answer the direct question, and instead, apologized and offered a refund for shipping it back.
My thinking is the new meter is off. I didn’t compare straight throw (lux to kcd) yet, but expect the new meter to be reading lower. His 1330B meters are the cheapest deal on them by far. They go between $30 to $50 everywhere else on eBay. I paid $35 for my 1st one. I really was thinking these may be factory rejects of some sort that are out of calibration. It certainly looks brand factory new though.
I always thought the sensor and calibration of these 1330B meters was a cut above the cheaper meters out there. I think manxbuggy1 reported way back his 1330B was about dead-on to his more expensive ExTech meter - might have been the LT300 featured in the PowerPoint linked above (I viewed it - nice!). He mainly wanted the ExTech for it’s more advanced features.
Not sure if Dale got together with manxbuggy1, but would have interesting comparing their 1330B’s. I’m pretty sure lights I worked on for manxbuggy1 in the past compared very close between his meter and my meter, and I thought the same was true for Dale and manxbuggy1 as well. That’s why I always thought #’s Dale post and #’s I post are very comparable in throw and lumens (same meter in the same range, same PVC light box).
You are talking lux though. Since I will have 10 of them I can calibrate lux to the average of the 10 meters. Our problem is sphere-design specific. We need a flashlight that is definitely 10 lumen so I can stick it in the sphere and say, look, that reads 60 lux. And another that is definitely 1000 lumen so I can do the same and say, look, that reads 10000 lux. Then graph all the data into a equation for the app.
We need rated flashlights. Not meters.
To clear things up, light meters measure lux. Lux is brightness at a POINT. Lumen is a measure of total light, so you need an integrating sphere to take it all into account and get TOTAL light.
+1, totally agree with djozz that’s it’s more important to have a “calibration” flashlight with consistent output, amp regulated/limited, like with a single 7135 for example, low power where heat is eliminated as a variable. A light that doesn’t drop output over time, not dependent on the cell used.
These meters/spheres scale well. If you have any doubts and want something in higher lumens, a multi-LED light like a SRK style with an amp regulated/limited driver might be a good choice. Keep the amps somewhat limited again to maybe 3-5A total, but driving 3-5 LED’s to get higher lumens. The BLF SRK 7135 based driver would be perfect for this.
I don’t really trust many of these so-called brand name, ANSI/NEMA rated lights - too many variables, and it’s been well proven one brand can tend to be high while another brand tends to be low. manxbuggy1 or rdrfronty first told me of this - probably has posts here on BLF describing it a while back. These guys take one light early on, maybe a prototype or pre-production unit, and send it out to be tested. Then things go into production, and who knows what changes. They don’t commit to say what specific tint or bin they use, so how can they assure keeping the tint and bin consistent from batch to batch? Each light doesn’t get individually tested, and you never see them update the specs unless it’s a full model upgrade.
NiteCore is a good example. I bought 2 identical NiteCore EA41’s at the same time, same model, and one was like a full 15-20% lower than the other. Nothing seemed to be wrong with the lower performing one, though who knows, maybe it was a defective driver or something, but had no other symptons accept lower output.
Good luck with this, if you get something working I would be interested in a purchase. I will reserve all my comments save one… If it doesn’t measure at least 5,000 lumens, I can’t use it.
What does this mean? Either I’m completely dense (a definite possibility) or I still don’t understand how you intend to calibrate these meter/sphere combos. Will my specific sphere be calibrated using my specific meter so that I’ll have my very own special calibration equation that just works with my pair, or will they all be calibrated together to an average value, so that some of our spheres read higher/lower than others just due to the averaging?
5K won’t be a problem.
It depends on test results. We them to be maximum accurate, and minimum complicated.
I think that probably goes without saying, but when it comes time to make an actual decision and go forward with a plan, I personally place much more value on accuracy than simplicity. A simple process that results in erroneous numbers isn’t very useful to me. But that’s just my opinion and this isn’t my project. At this point I’m just kinda along for the ride
Of course. But making decisions as a group without data was turning into ‘too many cooks spoiled the soup’ situation. And all that public theory bashing is creating fear in others. So I will be back with data.
Do you own or have access to a lab power supply? If yes, then you can calibrate the spheres with known bin LED’s. That’s how I “calibrated” mine, that along with some known output lights. But by the time I got to the lights after testing various LED’s I already had a very good baseline and the lights were really just confirmation.
And you’re correct about CC drivers, a linear driver would make it nearly impossible to get an accurate reading.
-Michael
Thanks!
-Michael
I agree, when I made the statement about heat not being a problem, I was speaking about actually shining through the opening, not directly against and through the styrofoam, I’m not sure that’s a good idea for a couple of reasons. One, getting a reasonably priced light meter that’s actually capable with an accurate V-Lambda curve is going to be difficult enough. Two, I’m not sure it’s going to be accurate reading through the styro, attenuation is going a problem, both with simple diffusion/dispersion and with attenuation of different light wavelengths. Third would be heat, direct heat against the sphere, depending on the temperature, could cause a whole host of other problems.
-Michael
Criminy guys. You are so sure it’s going to melt but you aren’t even discussing the right material. It’s NOT styrofoam. It’s high density expanded polystyrene. My hot BLF A6 does not even phase it when pressed firmly against it. And why would you press any light against the sphere?
LOL, I wasn’t saying it would or wouldn’t, I was only expressing CONCERN. Because I’ve melted things with my lights before. And not even the big hoss lights at that. We just have to use common sense and pay attention, that’s all. 
Edit: FWIW, “Styrofoam is a trademarked brand of closed-cell extruded polystyrene foam” Polystyrene melts under intense heat. And don’t spill gas on it while de-doming… just saying. And I think the talk about shining larger lights through the wall of the sphere conjured images of pressing the flashlight bezel against the wall, hence the concerns.
I trust that you are checking all the details and will create whatever means is necessary to make this work. You’re researching it to no end and seem to be of the mindset to make it as good as it can be. That works for me.