Texas_Ace BLF Calibrated Lumen tube / Sphere No math skills needed - Several spheres still available

He did send me some preliminary results and they were right in line with everyone elses numbers. Around .67 - .68. This is looking to be the target range.

I am going to go hunting today for some options to reduce the readings by that much. They have window tint film that blocks 30% of the light that should get the numbers really close, I am going to see if any local shops have some scraps I can play with.

Ok everyone. Good news, the lights from maukka showed up! Huge thanks to maukka for these!

So after testing them along with some other lights the numbers are lining up very well.

Like most I found .68 is the magic number.

So now to correct the spheres. I spent most of the morning looking at options and trying to get this to work in the simplest method possible. Including going to window tinting shops and getting some samples.

After a lot of testing I think I found a method that should work, I still need to test it on several more but the random sampling of 5 spheres I have been using are working well with it.

Even after sitting for awhile and being moved around several times and having these correction disks added they are all reading within my 5% goal (although 1 of them was right on the edge). I think I am going to raise the official specs to +/- 7% tolerance simply because I am sure there is an outlier that falls in that range and that is the Cree tolerance range anyways so why pretend that these can be more accurate then cree.

So the setup I am working with now are 2 of the diffusing sheets I used inside the sphere.

Depending which way they are orientated they can have a correction factor of .70 or around.66. So either 2% high or 2% low.

I think I am going to recommend going with the .70 correction factor and then simply rounding down your numbers since I recommend rounding them off anyways.

Plus I find that my sphere tends to drift a bit low every few weeks just due to dust and such. So that should balance out the readings to make them basically spot on since these will get dirty no matter how hard you try to not let them.

I am still going to try some other things but so far this is the closest I can get without having to stack 4-6 layers in just the right order and orientation of various materials. That is simply too much room for error for my tastes. Even how clean/dirty the disks are plays a noticeable role in the results.

The opaque diffusing sheet gets it really close with a single sheet but it is still around .65~~.66 one direction or .70~~.71 the other. It is simpler but slightly worse off.

Plus by sending everyone 2 of these sheets the spheres could be dialed in a bit better on a per sphere basis if a good “standard” light is ever made for individual calibration.

So opinions, how does everyone feel about a .70 correction factor?

Would you prefer .66?

Should I keep searching and find a .68 correction factor even if it is much more complicated leaving room for error?

If everyone agrees on a .70 correction factor I can get another diffusing sheet and get it laser cut this week and have it shipping out by next week.

Personally in my own sphere I will be using .70, it is good enough for me. I generally find that the simplest option is the best option. Plus since I round down anyways the numbers should be good.

Thanks for everyone having the patience to wait for a fix.

Close enough and I like simple

Good news TA! :+1: :beer:

I’m okay with .70 as we can round down a bit if necessary.

Do these sheets your talking about fit in front of the light meter? If so, it seems very important that it be thin. As the meter gets pushed out it effects the readings.

I just thought of something. If you use that sheet that gives a .70 correction factor we can add a tiny spacer to the meter to push it out a tiny bit and get .68. At least I can. Even a thin 1mm thick clear lense might give that bit of extra drop we need.

Yes, they sit in front of the meter and stop against the small lip inside the fitting.

They are thin enough to not effect the meter placement, the meter does not reach all the way to the back of the fitting anyways.

Although I did just realize that the 4” spheres could have an issue getting these disks to stay put as there is no lip on those fittings to hold them in. I will have to think on that.

Could possibly hot glue the disk to the meter itself but that is not as simple.

I am going to go grab a 4” and do some testing.

0.70 is fine for me.

TA, I was also meaning to ask you if your lumen tube was calibrated to match up to some of the other members on the forums homemade lumen tube/integrating spheres such as DB Custom, Tom E and Vestureofblood.

I was thinking they were all calibrated about the same, but DB was insulted that I thought his and others measurements might be 20% to 30% high. He said they based their calibration numbers on many high end lights rated ansi-fl1 numbers to arrive at a good average they believed was accurate.

I figured I’d ask you in case your lumen tube was not matched up to theirs.

Initially I did not calibrate my tube to match theirs and based it purely on the raw lumen numbers from naked LED’s. While it was not super consistent due to the china suppliers I was using at the time I was getting a calibration about 20-25% lower then I ended up with.

When I started comparing my numbers with all the others I could find on BLF I noticed mine were always very low, I just figured that the china suppliers had lied and all my samples were lower bins then I assumed and adjusted my numbers by about 21% it looks like on the notes.

Figuring that around 3 bins was a reasonable guess (seeing as I was buying “V6 XP-L HI LED’s” that did not exist) that put me reasonably close to the other readings I was seeing on BLF (although still generally on the low side). I was sick of constantly second guessing myself at this point and decided to just pick and number and stick to it.

Like Djozz said in another thread “The man that only has one watch always knows what time it is”. Well I decided to only have one watch moving forward and since it was still on the low side compared to everyone else, I just assumed it was reasonably accurate.

Turns out it was not even close. I am still shocked at just how far off it was. I never would of guessed that since it was not far off from all the other readings I saw on BLF.

Ok, I just did some more testing, I really like this setup for the 3” spheres, seems to be reading pretty consistent across all the ones I have tested.

I just started messing with a 4” though and it is a bit more tricky. There is no easy way to mount the diffuser like the 3” so the best option I am coming up with is to run a strip of tape around the edge of the meter and then tape the discs to it. It seems to hold them in place good enough.

Although them being closer to the meter causes the readings to be a little different. Still close but I will need a wider sample base to see which orientation will work best. Going to go grab the rest of the ones I have now.

It’s possible the other guys could be too high by a larger number than I thought. I suggested they might be 20% to 30% high, but they may actually be closer to 35% or so too high.

Have you considered loaning out those “Maukka measured” lights to some of those established guys with older devices? Maybe they would like to use it to see if their older calibrations are off.

Whoa…… very interesting indeed!! That ’might’ explain some of those super high lumen numbers. It would be interesting to know for sure.

So it would be great idea if any would do it. But it might burst some bubbles in the process if they did…… :wink:

If mine read low compared to some of them and it was over 30% high, then it is quite possible most of the spheres around here are 25-35% high or more. I am not going to point fingers though other then to point out that my own sphere was this far off before I had a way to calibrate it better.

I am considering making my own calibrated lights based on Maukka’s but I think I will keep the originals for myself so that I always have a consistent standard to refer back to. Never know what could happen if the post office gets a hold of it a few times.

If any of the older guys on here wants a loaner comparison light to calibrate their sphere I have a few lights of mine here I could measure and loan out though. I would just have to see what I have on hand that is regulated.

lol, yeah, my sphere is now the heartbreaker dyno (those in the car world know what I am talking about). I took a few random readings of lights I had laying around and it is amazing how much it psychologically hurts to see the numbers 30% lower even though I know logically they are the same brightness.

Ok, I tested a few more 3” and I am very happy with these, they are all coming out well within spec except for that outlier.

The 4” are also testing good as well, the first one I grabbed seems to of been further off then the others. The 4” is averaging out slightly higher readings but only about 1% or so.

Overall I really like this fix and by adjusting the direction that the discs are facing you can fine tune the readings if you get a calibrated light at some point.

I am going to go get the diffusing sheet this after noon and then see when I can get access to the laser cutter.

Yep TA…… it kinda leaves an empty sick feeling in the pit of ones stomach. :person_facepalming: :smiley: :smiley:

.70 sound good.

Hi.

I have done several readings on my lights and i feel that the number are coming in low. But its interesting to see how mych light is coming uot off my lights.

1000 lumen now is realy bright:).

If anyone want my numbers i can wright it upp but i dont know if it helps. TA_s fix will make them wrong…or nott?

/Micael

Right now the TA lumen tube is reading too high, so we take the numbers from the meter (usually after 30 seconds when using higher levels) and multiply by .7 to get true lumens.

TA is making a little disc that we add to our tubes to make them read about 30% lower. This means we don’t have to do any math. The reading on the meter will be the correct lumen output.

Correct, for the 3” tubes it will just be a matter of popping them into the meter hole in the correct orientation.

For the 4” tubes they will need to tape the discs to the meter in order to make them stay put. Not hard, just needs a strip of normal official tape to goa round the outside edge of the meter / discs.