I.S. is finally done

First I must say thanks to Match for posting this project and helping me along. I finished my IS pretty much according to the plan set out by Match. The only thing really different is the way I mount the Lux meter sensor. The lux meter I got from Amazon does not have a collar that will allow it to be press fit. I like my solution to that problem so all is good.

I have figured out the correction value and am very happy with the readings I get. I have been scouring the internet and BLF for known values of lights I own. I have it down now where I am very confident with my readings. Its really cool how I can get readings that match the numbers from other sources.

Here are a few pictures. All beautiful artwork is courtesy of my wonderful daughter who does these things for me every now and again.

If you are thinking of doing this project, do it. I had a lot of fun with it and will for a long time. Thanks again Match and everyone who piped in to help.

wow that looks great!

Beautyful and functional piece of art...

That's cool.

My luxmeter has been on it's way from Manafont for over 2 weeks now. Getting pretty impatient... Once it arrives, it's time for some paper (s)masching. Mine will not be that fancy, though. If I bother to paint it, it might get the classic Adidas Telstar style.

Very cool Michelangelo (Lang)!

I guess I should have said, "Very cool Michelangela!" :bigsmile:

Hei, this IS looks great! You can use it for flashlight but also like a decoration for any room in the house!

Great job!

Good job, Lang...and excellent artwork by your daughter! I'm glad it all turned out well for you.

Oldbob, this is the meter I bought from Amazon http://www.amazon.com/Mastech-Light-LX1010BS-display-Luxmeter/dp/B004KP8RE2/ref=sr_1_6?ie=UTF8&qid=1307479229&sr=8-6 It works well and is very sensitive. Kind of has that cheap hollow feel to it but it’s pretty nice for the price.

Nice Job Lang! Im coming over to test some of my lights.

Good because I ran out of lights to test. I don’t have Dons collection.

I got my luxmeter, finally. It took 3 weeks from Manafont, the longest ever from them. As soon I as got some motivation, I will glue together my own I.S.

I know this is an old thread but I was wondering if there are any more Match inspired integrating spheres out there. How about other ideas. TurboBBs idea is really cool with the PVC pipe. Does anyone else have any good contraptions or ideas they are hoarding?

Ooh! I didn't even know this thread existed (have a lot of catching up to do over here). That is friggin awesome!!

Truth be told, one of the reasons I went down the pipe route was (and aside from the hassles of calibrating the baffle, etc) my wife tolerates my hobby as is, I knew for sure she wouldn't deal with a 20"+ IS sitting in the office. However, I had no idea how big 4" pipes w/3 elbows would be either but it's still more compact than an IS and I can hide it away in the closet.

HOWEVER, had I knew of this thread, I might've ended up doing an IS and having the kids decorate it (which mother wouldn't want to display their kids artwork?) so I can use it as an excuse to keep it in the office room...

Thx for bumping this thread! I still might end up working on an IS just yet.

I bought the same meter lang has (match reccomended) a long time ago and I need to break down and just do this. The thing is; I'm somwwhat happy with my current method of relative brightness measurement.

I fear this is going to sound unbelievably naive and well on to stupid but here goes anyway. And, I guess I just need my lame theory shot down so I don't go on believing incorrectly.

It seems to me that any integrating sphere, especially home made, will measure the test light relative to how dark the sphere is. That's why it must be calibrated and/or we make our adjustment relative to a light with a known lumen output.

So, what's the difference between that and measuring against whatever ambient light there is in the room? A 980L is going to be just as much brighter than an E07 whether it's dark, semi-dark or pitch black, no?

Right now, my office measures 59 from where my light meter is. One of my L2Ps with an UF XM-L measures 175 and my Dry measures 413 and steps down to 267. Won't these relative differences be the same using a sphere?

If I get a light that claims X lumens, no matter what time of day it is I can easily measure how bright it is, relative to another light - as long as the base reading remains the same. That's how I knew how much my Sky Ray sucked. Both E1320 breathed-on F15 and C88 measure 210 while the triple XM-L Sky Ray does only 240.

If I had a formula to figure the difference, who needs an IS?

Okay fellas; I painted a target on my back . . .


Foy, I'm in your camp on this one but isn't having you own homemade I.S. cooler than having a ceiling? The proper nerd in you needs an I.S. so you can try to explain to people what it is and why you have it. Flashlight nerd cred.

Yeah. I don't know what I was thinking. And, yours turned out so awesome.

I can tell too, in my reviews; nobody cares about my lame "relative" measurements. If I can't produce an accurate lumen rating from an IS, I'll never be taken seriously.


Edit: Short answer is this - The point of an integrating sphere is to equalize the readings regardless of beam profile, whether it be a flooder or thrower. The reason it's typically a sphere is because its the best geometric shape for this function.


Your reasoning partially correct, but does have a few fundamental flaws. Not sure how this explanation is going to come out, but I'll give it a go (with the help of my good friend, Caffeine :) ) :

* There are actually two mathematical variables to this equation: Correction factor and Offset. I believe what's happening is that you're mistaking the offset for the correction value.

* The correction factor you are looking for in an I.S. has nothing to do with ambient light. Ideally ambient light should be zero, but even if it's not (aka not a perfect seal around the I.S. entrance) it's still a static value that is subtracted from the final calculated result. Imagine the following:

Let's say your office is a perfect I.S. due to your explicit design parameters given to the general contractor (he still thinks you're nuts btw...). The only problem with this I.S. office of tranquility is that pesky window your wife penciled into the blueprints while you were out test driving the new Camaros. Even if you test your lights only at night after watching reruns of The Sopranos there is still a little light coming into the room from your crazy neighbors Christmas decorations he leaves up all year. The good thing is, the value of this light is static, i.e. constant and never changing and the amount will be subtracted from your total value. If the amount is 15 lm, that amount will be subtracted from the total of any light you test in your office regardless of any other variables (that is of course, until you make a phone call to cash in a favor and that "problem neighbor" ceases to be a problem). A 115lm reading from a pen light will give you 100 actual lumens and an 815lm reading from a superthrower will give you 800lm and so on...

* The variable we're really concerned about though is what I've been referring to as the Correction value. Ideally this value will be constant independent of the light source. The main factor in helping keep this value constant across all shapes and beam sizes is how well your sphere integrates the light. The difference between this and offset is that this value is a coefficient in our lux to lumens calculation. If all of the light from a source isn't integrated properly, the accuracy of our readings will deteriorate proportionally as the lux value increases from brighter lights. Let's try a more realistic scenario now:

Let's say your office has to be the more mundane cube shape because your missus didn't want this big sphere attached to the house due to the annoying fact that neighbor kids might mistake it for a mini Epcot Center (grumble grumble...). Because you're an understanding fella, you make this one concession (you still get the new Camaro though). The walls are a pleasing hospital white along with the ceiling, and the decorative motif of the day is based on 19th century institutional minimalism (without the padded walls of course, they're tacky).

Now there is no window (but even if there was, we now know how to compensate for that) and you set off testing everything from a new Dry to the Olight SR90. You calculate your correction value based off of your beloved Ultrafire 980L (My Precious...). Everything is going well until you start noticing discrepancies in your data. The thrower lights amongst your vast collection seem to be reading spot on (pun intended), while the floodier lights seem to read lower than expected. This is because the throwers are benefiting more from the ceiling bounce that a comparative flooder, which must rely on the walls to help get some of that light back to the sensor. Here's where integration matters. On lower powered lights the difference may be chalked up to lackluster manufacturer's tolerances...but as the output of the light increases this error will become exponentially larger and may drive you to put a hit out on your general contractor and a slew of overseas light manufacturers for false advertising...

* A close to ideal test of any apparatus used to ultimately measure lumens would be this: Measure a bare emitter at a known current, then place a smooth reflector over that emitter and measure again. If the results are fairly close (there will be a slight loss from the reflector) your I.S. works. If on the other hand your results favor the reflector over the bare emitter, the light is not being properly integrated and any results obtained are most likely as meaningless as my ramblings...

**Disclaimer: This was typed while treating a head cold with coffee and vodka, along with the fact that my academic background lies in nuclear/electrical engineering and not optics. In other words, I may just be talking out my arse...

That was a very entertaining read , Match .

Nice Match! I was amused and educated. Epic.