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

RE:accuracy.
The way I see it is more important for these to match up to TA’s #s and be consistent from one sphere to the rest.

My main goal, and many others I would guess, is to have a way to compare my builds to others here.

As well as before-after on my own to see if changes had the desired/expected change. Also to have measurable numbers for my builds, rather than guess which of mine are brighter.

Just my $.02.

So these buyers are going to have their own unit of measure? Better reference it as such so your peers will know :smiley: 1,500 TAlm

I would guess a pretty significant jump depending on the phone. Most phone lux sensors are crude at best.

The old shoebox setup also tends to be susceptible to beam shape changing the numbers, that is what I spent a lot of time trying to get rid of with this setup be using the diffusing sheets.

That said, if you have a good standard to calibrate a sphere, a lot of things will work. It took me hundreds of tests and over 6 months to get a good enough “standard” to trust it.

The thing that really makes these better then home made setups is they will all be calibrated the same way and use the same setups, thus allowing them to be comparable to each other. The calibration is a big part of the selling point if you ask anyone that has made a DIY setup.

Also over time my numbers have shown to be inline with many others here, generally leaning towards the low side compared to others.

I know I would of happily and gladly paid twice this price in retrospect to get a pre-calibrated sphere but I am selling these so take that with a grain of salt.

I would suggest all who buy these Units measure a few lights they own—-write these measurements down as calibrating reference—this will tell you if things get off in time—mainly when the meter batteries get weak—meters tend to do crazy things with weak batteries—-even high dollar Spheres have a calibrating bulb—my old hickok tube testers have an included calibrating tube——Just my 2 cents—-LOL

Yep, this is a very wise idea. I did this same thing and I have 2 lights I use to double check my sphere on a regular basis and a bunch more written down for more in depth tests.

The biggest issue I have had with readings changing over time is dust, it will collect and lower the readings naturally.

I clean off the top and it is back to normal.

5% difference between meters is pretty reasonable.
I assume you calibrated your spheres and tubes using the manufacturer values of flashlight lumens?

Some time this summer I’ll ask the optics department at my university if I can use their integration spheres, they have a 1m and 3m.

Ok, I am sorry to report that I made a mistake in the order and it will take a week or so to get the correct parts.

Long story short, they do not have a 4” to 1.5” reducer so I had to use a 4” to 2” and then a 2” to 1.5”.

I had 2” on the brain and ended up having to place the order over the phone due to some website issues at the time and I mistakenly ordered 3” to 2” reducers for the 3” spheres instead of 3” to 1.5”.

I also totally forgot to order the 2” to 1.5” reducers.

So I am placing an order for the missing parts this weekend and I expect them to ship on Monday. Last time they arrived on Friday so I expect the same this time.

In the mean time I am preparing all the other parts and using some pieces I got from home depot to do an initial calibration of the spheres.

This should make it fairly quick once the missing parts show up. I am hoping to make my 4 week deadline I set for myself.

Today I got the family involved and we got a fair amount done in preparation for the real work. Hoping to start really digging into them tomorrow.

I will keep ya’ll updated.

I can say that I will NOT be selling any more of these for this price again.

Just got the order placed for the missing parts, they say delivery is expected Friday.

I got a payment earlier today for a sphere but there was no user name on the payment. Could whoever sent the payment please reply to the PM I sent you so I know who it is from? Thanks.

Ok, almost a week and countless hours of work later and I officially have the first sphere calibrated and put together!

It has been way more work then I planned on to get these sorted out. I went through a dozen different options to get these sorted out but in the end it is just a matter of trial and error on each sphere.

All the parts are here now.

So the next several days are me putting together a bunch of spheres and calibrating them.

On the plus side they are matching mine very nicely once calibrated. Looking like I will be able to be well within the 5% tolerance range I was hoping for, I am aiming for 3% between spheres. Getting closer then that is very difficult as even details like how hard the pvc is pressed together comes into play at that point.

I’m def in…

PM sent.

Also just so everyone knows, I had to raise the prices on the spheres for new orders, after calculating all the costs involved both monetary and time, the existing prices were just not worth it.

For example I just had to spend $60 to buy boxes to ship these in, on top of the shipping costs being a lot higher then planned. The little things add up quick.

Not to mention the time involved, it is taking around ~2-3 man hours per sphere start to finish to get these ready, that is of course if you don’t factor in the 6 months I spent setting up my own sphere to get the design and calibration.

The new prices are:

3.5” - $135 + $17 S&H in cont US

4.5” - $200 + $25 S&H in cont US

I will be putting up any that are left over on ebay for $150 + shipping and $225 + shipping respectively to cover the ebay fees.

Now since I did not give any warning on the price increase, anyone that wants one today I will honor the old price.

If you have to take money out of your pocket to send my to Sweden send me an mail and i’l put in som more money.

Thanks, I will let you know when I get to shipping them. Thus far just been going off general calculations, things are usually a bit different once you ship the real things (sadly usually higher).

I am still working on the spheres, had to change the way I was doing them a few times, so you will notice that the centering rings were painted silver as an attempt to make it look better then the reflective tape, but that didn’t work lol.

End results are I now have about 15 spheres mostly ready, just have to double check them and then glue them together. We are tripping over spheres in the living room lol.

I am hoping to start shipping early next week if all goes well.

After a lot of work they are lining up with my own sphere quite well.

Now Back to work….

Thanks for all the hardwork. Even with the new pricing, it is still a good value. Now forum members around the world have a standardized method for comparing their flashlight brightness with other flashlight enthusiasts.

What he said :slight_smile:

Ok, after a solid day of work on these spheres I have 12 finished, in boxes and ready to ship.

About half of the remaining 3” spheres are done with the “1st stage assembly” and another half is done with the “2nd stage”. It is complicated, way way more complicated then I planned on. Each and every sphere has to be calibrated individually sharing very little of the process with the others.

I was really hoping to have a “recipe” for them that would get me within 5-10% and then just fine tune from there but that is not the case at all and for the life of me I can not explain it. I tried to figure it out for a whole day earlier this week and just got frustrated lol.

Gonna take tomorrow off for Mothers day.

Could some of the problem be that white PVC pipe isn’t made for reflecting light and therefore the illumination tolerances across tubes are not uniform. Not that you can’t make an accurate lumen measuring device out of one, just that across materials non-uniformities can create the need for the calibrating you are describing. Sure they all look perfect white to the eye inside, but I wonder if the inside surface of the pipes are optically dissimilar in small but significant ways.

It won’t matter for the final product, as you are calibrating them, but as you mentioned…takes more work than to just slap them together…

Interesting finding on your part. Curious how singular lumen tubes made by people can compare with each other’s.

At least your batch will all be giving similar readings to all the people that bought yours—a true standard!

When I put my name on the list (#5), I assumed it would take a while. I was prepared to receive it anytime in June.

You're ahead of my expectations.

This is quite probable. As 2 seemingly identical pipes can have slightly different readings. In some cases the ones that you would swear should ready higher will actually read lower and vice versa. I have given up on figuring out any rhyme or reason and just go at each one by trial and error until I get it dialed in.

You bring up a point that leads to a pet peeve of mine actually when it comes to lumen numbers posted in the flashlight world in general.

Anytime I see something like “light A made 846 lumens” I just laugh, there is no way in heck that a DIY sphere is anywhere close to accurate enough for that kind of reading. Some are better then others but even the best I would not put better then 10-20%.

Technically all Cree LED’s we use have a 14% tolerance from cree, meaning that no sphere can be more accurate then that. The flashlight driver/batteries ect add even more variance issues on top of that.

This is why you virtually never see exact lumen numbers from me, I always round them (usually down). I like my sphere and I think I have it reasonably well calibrated but I am under no delusions that it is still a DIY home made PVC version of a $10k sphere. These are NOT precision devices.

I would recommend and ask that people using these also round the numbers so as not to give the allusion that these are more accurate then they are. Posting exact numbers down to the single digit makes people think you can actually get a reading down to the single digit.

So back to the original question, from the comparisons I have made and looking at others (My and Djozz talked about this a few years ago) the DIY spheres you see in the community vary widely. 15-40% variance is common from sphere to sphere.

A lot of this comes down to calibration method, flashlights are simply not a remotely good way to calibrate a sphere, you have to take hundreds of readings and average them out to get something even close to a reasonable calibration. That assumes you can trust the manufactures ratings in the first place (which unless they measure each and every light, still has a 14% tolerance for the LED itself).

LED data sheets are much more consistent since Cree has a big motivation to get the numbers right but still have a 14% tolerance range built in.

So in the case of these spheres, I calibrated them with LED datasheets, this means at the very best they can be ~14% accurate to actual lumens since that is the tolerances on the LED’s themselves. The end result can not be better then the calibration method. That is simply how things work. This is why professional calibration LED’s cost thousands of dollars.

I would add a few more percent to that range as naturally there are more tolerances to take into account besides the LED’s themselves, such as heat, power supply variations ect.

Now consistency is another item altogether and that is much much better. People like to confuse consistency and accuracy. On my sphere I have a few “standard” lights that I will regularly check the output on (the same lights I am calibrating the new spheres with) and over time excluding dust build up, I get maybe a 1-3% variance at most (although I would officially rate it at ~5%). This is mostly due to the atmospheric conditions like humidity and such.

The spheres themselves seem to be coming out to well within ~3-4% on initial calibration compared to each other here. Figure that needs to be widened some once the post offices gets done with them and they are put back together but still very comparable. So the most important thing is the consistency between them as you said.

I just don’t want anyone being under the delusions that these are precision instruments. For that you will need to spend 100x the price.

Years ago when I was researching building one of these I recall people were painting the insides with flat white spray paint, I wonder if this was the reason for doing it?