The Legendary BLF Integrating Sphere starts here! (Delivered)

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emarkd
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djozz wrote:
Sending one of them off for a certified calibration is the expensive way.

If one sphere was sent out for certified calibration, could that one sphere then be used to calibrate the rest of them?

djozz
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emarkd wrote:
djozz wrote:
Sending one of them off for a certified calibration is the expensive way.

If one sphere was sent out for certified calibration, could that one sphere then be used to calibrate the rest of them?


I’m not aware of places where they certify spheres. And you can’t couple one unique number to an integrating sphere like this anyway because the number that the luxmeter gives is not independent on the physical appearance of the light source.

It is much more robust to have a constant light source calibrated, and a calibrated light source is more practical too, i.e. if you decide to alter the sphere design it is very easy to re-calibrate it.

emarkd
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djozz wrote:
emarkd wrote:
djozz wrote:
Sending one of them off for a certified calibration is the expensive way.

If one sphere was sent out for certified calibration, could that one sphere then be used to calibrate the rest of them?


I’m not aware of places where they certify spheres. And you can’t couple one unique number to an integrating sphere like this anyway because the number that the luxmeter gives is not independent on the physical appearance of the light source.

It is much more robust to have a constant light source calibrated, and a calibrated light source is more practical too, i.e. if you decide to alter the sphere design it is very easy to re-calibrate it.

Ah, my misunderstanding. I see what you mean now. Thank you.

DB Custom
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I do Jos. All the time. Wink Like a reference manual, you and Match.

When manxbuggy1 and rdrfronty built my PVC trap box (and their own and TomE’s and Richards) they used 20-30 factory ANSI rated lights and averaged the results. Both are/were collectors and had a variety of lights to work with, manxbuggy1 preferring smaller hot rod style lights and rdrfronty going for a host of name brand large lights by Nitecore, Olight, Fenix… all the big favorites. So there is a wide assortment of test subjects with a background of good ANSI ratings used to get our multiplier.

emarkd
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I still don’t know much about this sort of stuff, which is partly why I’m involved in it. I do have a “light box” built from an amazon shipping box. I cut a cardboard baffle, taped it into place and spray-bombed the whole inside white. Two holes in the sides and it was done. Its…okay, but I can actually make my results vary by as much as 10% just because the walls are too flimsy to hold the light and the meter still. Just a bit of tilt one way or another and the numbers fluctuate. So I want something better. I calibrated my box using some of my own factory lights, which I do have a lot of … about 100. Many are modded and useless for this sort of stuff, but many aren’t. So again I’m happy to loan anything I’ve got for calibration purposes.

But I do like the idea of sending a light off for true ansi calibration, which could then be used to calibrate our spheres. I’d be in for my part of the costs of that, assuming its not outrageous.

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Don’t fret guys, we will use whatever uniqueness is required to get impressive results. That’s why I need lots of data, so I can know and compensate. DB Custom, yes, averaging many lights would be awesome. Who do I PM to ask about borrowing them? I didn’t quite follow who owned them.

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Guys, how big of a hole do we want? Would a single 2” work? Please share some models and head sizes.

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2” diameter works out to be 4.9% 1.0% of the total area within the 12” ball.

According to manufacturer, the walls are 7/8” thick, so the internal radius is 5-1/8”. Internal sphere surface area is 4 x pi x r^2 = 64.4 330 sq. in. Area of 1” radius (2” diameter) hole is approximate 3.14 sq. in. Doing the math, that comes out to be roughly 4.9% 1.0%.

Note: My wish is for a 3” diameter hole. That works out to be about 11% 2.2% of the internal sphere surface area. I know that this is bad. Just stating my personal preference.

The 3” diameter hole would accommodate my flashlights up to the head diameter size of a Thorfire S70.

A 3.5” diameter hole (2.9% of internal sphere surface area) would be even better. It would accommodate my Nitecore TM16GT.

Edited in bold typeface.

Rule 1-1 as it applies to life, take it as it comes.

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Although a 2”/50.8mm is in the best size range for accuracy I would be OK going very slightly larger if that’s the “vox populi”. I don’t think it will be a big problem going larger since we’re not talking ‘lab grade’ expectations. 2” gives just a little clearance on my largest C8 clone, so I’m good with it.

Phil

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1dash1 wrote:
2” diameter works out to be 4.9% of the total area within the 12” ball.

According to manufacturer, the walls are 7/8” thick, so the internal radius is 5-1/8”. Internal sphere surface area is 4 x pi x r^2 = 64.4 sq. in. Area of 1” radius (2” diameter) hole is approximate 3.14 sq. in. Doing the math, that comes out to be roughly 4.9%.

Note: My wish is for a 3” diameter hole. That works out to be about 11% of the internal sphere surface area. I know that this is bad. Just stating my personal preference.

…think you left out a ^2 there. A 3” (diameter) hole is only about 2% of the surface area of a 5.125” (radius) sphere.

emarkd
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I thought the whole point of using the larger sphere was so we could have a larger hole and therefore test larger lights. I was definitely hoping for a 3” hole. That covers bigger hosts like the Maxtoch M24, Olight M3SX, even barely some stuff like the big Thrunite/Acebeam lights like the TN32, etc.

But I know nothing about all this. I already see where djozz says 3” is a bad idea (why? too much missing interior surface?) so if its a bad idea then do the good idea thing. Having a 3” opening is pointless if the results aren’t trustworthy. I’ll be happy with whatever comes, as long as it works.

SawMaster
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Didn’t do the math, but I’d be OK at ~7% at the most with 5% being better, but 2” or 50mm as the minimum regardless of the foregoing.

Phil

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DEL wrote:
1dash1 wrote:
2” diameter works out to be 4.9% of the total area within the 12” ball.

According to manufacturer, the walls are 7/8” thick, so the internal radius is 5-1/8”. Internal sphere surface area is 4 x pi x r^2 = 64.4 sq. in. Area of 1” radius (2” diameter) hole is approximate 3.14 sq. in. Doing the math, that comes out to be roughly 4.9%.

Note: My wish is for a 3” diameter hole. That works out to be about 11% of the internal sphere surface area. I know that this is bad. Just stating my personal preference.

…think you left out a ^2 there. A 3” (diameter) hole is only about 2% of the surface area of a 5.125” (radius) sphere.

Thanks! I was in a rush to pick up my son after school, didn’t get a chance to check my calcs.

And I’m simply drained from discussing his school problems. Everything is the teacher’s fault, she sent him to the principal’s office for “no reason”, he was just studying at the time like he was supposed to. Some/most of his fellow students are mean to him, but he’s never mean to them. Nothing is ever his fault.

Sometimes, being a parent isn’t much fun.

Rule 1-1 as it applies to life, take it as it comes.

Joshk
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Ok. I will plan to taper the 2” hole, so as long as the BEAM is 2” or less you are golden. The head can be a bit larger than 2”.
I received the 1/2 sphere they had in stock just today. I have to say, shining a 1400 lumen flashlight from the outside in lights the interior evenly and perfectly. Shining it inside is too intense. I think we will stick with the 2” hole for low lumen work and use the through-wall method for high lumen work. There won’t be a hard size limit for through-wall. From what I have seen, we are on track for excellent results!

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For the “thru-wall” readings is it going to be necessary to center the light on a specific spot? If so, then that spot should be accurately marked permanently somehow. Consistency between all users is what makes this project different and so valuable to us.

It would also do well to include usage instructions (could be posted on BLF somewhere) so that everyone knows how to position the light being tested correctly, to allow 30 seconds runtime before getting the reading, etc.

Phil

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Yea I plan to mark it. There will be a video too.

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Joshk wrote:
Ok. I will plan to taper the 2” hole, so as long as the BEAM is 2” or less you are golden. The head can be a bit larger than 2”. I received the 1/2 sphere they had in stock just today. I have to say, shining a 1400 lumen flashlight from the outside in lights the interior evenly and perfectly. Shining it inside is too intense. I think we will stick with the 2” hole for low lumen work and use the through-wall method for high lumen work. There won’t be a hard size limit for through-wall. From what I have seen, we are on track for excellent results!

According to this lumens-to-lux calculator, for a 5.125“R sphere (area = 2.29 sf), it would take over 40,000 lumens to exceed the LX1330B’s 200K lux range.
http://www.rapidtables.com/calc/light/lumen-to-lux-calculator.htm

Granted, that’s a theoretical calculation.

In our model, we’d have an adjustment factor that could be higher or lower depending on how the light is collected within the sphere. However, I’d suggest that it is most likely that the sphere could accommodate a beam of 10K to 20K lumens without fear of overtaxing the light meter. The higher meter range might be less accurate than the lower range, but it would probably be more accurate than using the through-wall method.

With that in mind, I’d suggest that the 3” diameter opening still be considered for discussion.

Rule 1-1 as it applies to life, take it as it comes.

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The problem with a 3” head inside the sphere is the beam angle crawls up the wall so far. The meter starts seeing the outter hot spot. Through-wall is totally solving that I see.

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When you cut out the hole would it make sense to save the plug that is removed? That way you can reinstall it and have a solid sphere for the shine-through-the-wall readings?

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Yep, that’s one reason for the tapered hole. The plug will push right back in.

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Okay, so then do I understand correctly that the sphere will be set up to do “direct” readings through a hole for most lights, up to a certain size (which may or may not be 2”) but that it’ll also be capable of measuring larger lights through the styrofoam wall? I would assume then that there would be two different calibrations, cause the “through-wall” reading should be quite a bit lower than a “through-hole” reading.

So what then do we expect to be the maximum size this sphere could be used for in some way? Would I be able to read, for instance, a 4” diameter light with it?

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My largest is nearly 5” and it looks good.

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This is great, I tried to get the guys at CPF to do this years ago, when there was a member there who had access to a sphere at work (MrGMan – GMan?). This is the best way to go about this, have someone build a light source, have the lumens certified at different levels, and calibrate other spheres. What I suggested then was everyone chip in and build a light source, either a large bodied flashlight with CC regulation or, more preferably, a heat sinked emitter. The latter would have required users to have a lab power supply, or shipping one around to the different participants. The former would have required shipping the light, charger and batteries around. Not to mention everyone would have been responsible for building their own sphere. This way is much simpler for people who don’t have the time or equipment to build their own.

I don’t know about here, and I haven’t read past page one yet, but over there we got plenty of naysayers. Don’t listen, it’s a great idea, and while they may not be true IS’s, you can obtain readings which are repeatable, reliable and very close to an actual sphere or light output.

I built a light box, not even a sphere, when I first started in all of this and the readings were very surprising, right in line with manufacturers specs. And all that was before I built an actual sphere and bought an NIST light meter.

I have some PowerPoint presentations that might be interesting, they’re over the accuracy of off the shelf light meters and how modern LED’s affect the readings. They’re from a couple years back, and I’m not sure how I’d go about converting them and posting here, but I’m willing to give it a shot if you guys are interested?

Again, Great Idea!

-Michael

BTW: Here’s the old thread where I built my first light box, and the readings matched the manufacturer ratings closer than expected for a cheap meter and simple box.

Interesting Light Box Numbers…

ETA: Made it to page 2. Those saying the sphere needs to be bigger are correct, especially for the types of lights built around here. I believe mine is 16”, but all my stuff is packed away in boxes in storage. The balls can be expensive, but I’ll look for the link where I purchased mine, IIRC I paid around $36-38 shipped. Also, don’t forget to account for the thickness of the styrofoam in your calculations, for instance, a 16” ball may be 1” thick, thereby reducing the inside diameter.

Hole size on mine is around 2-1/4 or 2-1/2 inches IIRC, it would accomadate most lights but not some of the bigger multi-emitter lights or even some large reflector lights I have, one of the Lowes Taskforce lights that was posted as a deal here a couple of years ago, or some of my (comparatively) small handheld spotlights . Maybe I’ll start over and build another sphere, I’ve put new emitters/drivers in some of those and some are in que to be modded again with new LED’s, it’d be nice to be able measure those.

And to be inline with ANSI there is a small waiting period before taking the measurements. But unless it’s uncomfortable to hold your hand in front of the light for a short period I don’t think it’ll be an issue. With hotwires definitely so, not so much with LEDs. I’ve got some that you can feel heat with your hand in front of the reflector, but nothing hot enough to melt styrofoam. I would think the greater danger here would be in an extended runtime test, where the light itself became too hot to touch or hold, and if it was in contact with the edge of the opening might cause a problem. The meter I have is an Extech 407026 , it’s a data logging meter (if you have the cable and software) and when I’ve done extended runtime readings I’ve used a small PC type fan to keep the temperature under control, both for the light and sphere.

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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?

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djozz wrote:
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

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Great stuff happening! Smile

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! Smile ) so I’ll report on my findings on how that impacts the readings.

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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.

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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.

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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).

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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.

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