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

Hi
I am so glad that see you have made this type of LumenTube yourself
But I have some questions that maybe you like to answer me
First : Is anyone else made lumen tubes lnstead of lumen speheres? In Theory I think that you are right, But I just want to know , is this typical or is it your invention? and did you test it and what was the result and accuracy?
Second : In British standard, As I remember, It says that Lumen Sphere’s paiting must have more than 90% reflectivity , And I have searched and found that only paints based on Barit can have that reflection , and paints based on Titan have less than 85% reflectivity , Now I like to know, did you paint inside of yourtube? and Is it isolated from outside?
Third : I want to use this lumen tube idea for Luminaires that are generally much larger than flashlights , Is it possible to change the plan , so it can fit larger lights , and does it result well for all types of luminares? (for example wide beam or narrow beam ones as well)
Fourth : Is it possible to use standard LED Diffusers as diffuser?
Thanks alot for reading.

Texas_Ace did not invent this type of device. They have been built over the years by lots of people, but TA has refined it by adding diffuser panels which really helps to blend the light better. Usually people build lumen tubes or spheres theirself and you get a lot of variations, some of which are not so good. TA made several based on a template so a lot of people could have the same design and get better accuracy. If you plan to build your own, you will want to get a calibration light to test it. You will also need to devise a way to change the opening size if it’s for a flashlight.

It has the bare plastic white interior. No painting is used. You dont have to worry about light getting in from the outside.

The tube design works well for flashlights. It can capture the light and mix it up, integrate it, before it gets to the sensor. I’m not sure what a luminare is, can you explain?

If it’s really big or spreads light from several directions you may have to use a different design, such as a sphere or similar.

You probably can, as long as it spreads the light evenly. TA used a certain type and number of diffusers so the lux meter displayed the lumens with no math involved. This is a nice feature and makes measurements faster.

Late to the party, but I’d like one if still available. Thanks.

TA….you use black tape for tube calibration, right?
Thinking about spectral response errors that all cheap meters have gave me an idea - could we compensate for the errors by callibrating with a carefully chosen paint?
F.e. let’s assume that your luxmeter redponds too strongly to blue light (it likely does). A greyish-yellow paint would absorb more blue than other colours, possilby reducing the error. Am I righ”t?

No need for colour, any white diffusor will remove some blue light due to scattering more than other wavelengths. Light that has gone through the white tube has warmed up too, but will that be the right compensation for a luxmeter with spectral arrors, who knows? :slight_smile:

Yes, this is possible in theory.

Although actually making this work in practice would be very difficult and would need a lot of testing with spectrum analysis.

A filter could also possibly work but same issues with testing and getting it to work properly.

I find just rounding up with warm LED’s and rounding down with CW works good enough.

Scattering is directly proportional to wavelength. LX-1010B which I take as a representative “cheap meter” has many times too high sensitivity for 440 nm. Warming up by going through the pipe? I guess that you mean that pipes are not pure white but slightly yellow right?

What would it take to try to apply a measured correction? I’m not sure but I’ll write down how do I see it.

1. Prepare:

  • a tested luxmeter with a known spectral sensitivity curve
  • incan bulb
  • spectrometer
  • 2 integrating tubes

2. Measure the spectral error introduced by the tube.

  • (optional) do it at various points of the exit to ensure that the tube integrates well

3. Multiply the spectral errors of luxmeters and the tube. This gives the total error of the tube. Take a negative of that - that’s the ideal corrective colour.
4. Go to paint mixing company. They’ll use software that calculates the optimum blend of a dozen of pigments to produce spectrum that matches your as close as possible
5. Apply the right amount of paint to compensate for the spectral errors (I don’t know how to determine that w/out comparing that tube with a reference)
6. Then - tune with black tape.
7. Apply the same amount of paint to the other tube. Test it.

Yes, it’s a lot of work.
But if it produced improvement that could be blindly applied to other tubes of exactly the same construction, that might push a budget tube correctness up.
Would the effect be significant? I have a hunch that if it was then integrating sphere companies would be doing it already, seems like simple paint + simple filters would be cheaper than the whitest paint + sophisticated filters.

So…I’m not sure if this idea is good at all. And I’m not sure how would one implement it. But the potential improvement seems nice to me.
And maybe someone knows better and can improve the cost and value estimations. :wink:

I expect that most paint pigments affect more than one region of the visible spectrum so that it is impossible to create a combination that produces a tailormade absorption spectrum. It is probably why good luxmeters are so expensive: it takes exotic materials to produce a filter with an exact absorption spectrum.

I was going to say basically the same. While a good idea on paper I have a feeling it would be quite difficult to make it work in practice and would net you other oddities. Such as I foresee different tint lights having the lumen skewed due to the paint absorbing more from one LED then another.

Putting us right back in the situation of having to round the number up or down to account for it.

Don’t get me wrong, it is a good idea and would be cool to test but we are talking dozens of hours of testing with some expensive equipment that most of us do not have at the minimum. That is a lot of time for what amounts to an almost unnoticeable to the human eye change.

Fair enough. :slight_smile:

I started a new thread about using the Texas_Ace Lumen tube to post measurements in reply to BLF member requests for specific flashlights.
Here:

Thanks to T_A and all who put in so much work making the “Tube” a thing.
All the Best,
Jeff

If this is already being done some place. Let me know and I’ll edit my POSTs to fix it.

Spamming is not allowed in this forum.

This is not spam, I just recommend what I think is good seller

You signed up to this forum and your very first post was a bunch of links to this company?

How did you even find this topic? It is 6 months old. Are you a flashlight person or did you just search online for people talking about PVC pipe? You realize this looks highly suspicious, right? This is the exact same behavior that a lot of spammers use. I just want you to be aware of that.

JasonWW, just go to one of the links and on top of the page click on "about" the company. That company's name looks very similar to the poster's. Coincidence?

I am going to start building my own rudimentary lumen tube based on ideas from this and Matt smith , and others.
I was hoping to find out what material was used for the diffuser sheet in the junctions of Texas Ace’s version? Or what could be used in place of his diffuser sheets if the material he used is difficult to source?

Thank you in advance

Technically you can use a lot of diffusing sheets but the readings might not be as consistent. This is ok if you know to adjust for it but was not good enough for me to sell to others naturally.

The sheets I used were from a local shop, I think that they were used as lighting covers but I could not find the same thing at home depot. I tried a few of the ones I did find at home depot/lowes first but they did not diffuse the light enough and that led to inconsistent readings between floody and throwy lights.

You might get lucky and have a better selection at your local store though as I only had 1 option from home depot and another from lowes when I was testing (looked like they had places for more but were out of stock).

All that said, cutting these sheets without a laser cutter will be a real pain, they shatter with most cutting methods I tried so it is real hard to make them seal, they can still work but be prepared for some hassle.

Another option might be to use some DC fix film and apply it to some form of plexiglass, assuming you can get a circle cut out of it.

There is no way I would of tried to make these without access to a laser cutter that is for sure.

TA - thank you for this info! As i got halfway through reading your response i had the thought “what about dc fix on 1/8” plexiglass?” LOL, so i’m glad you mentioned that. That is probably what i will try for multiple reasons -

1. I do not have access to laser cutting or if i do it is too much legwork. unless i absolutely have to, in the event dc fix doesn’t work well enough.

2. I can cut plexiglass with my bandsaw (keeping the wrapper on it or cover it in painters tape to avoid scratching it on the saw’s table).

I had just assumed it was some diffuser material you had someone specifically engineer for the measurements of the tube. If that is not the case, and it doesn’t sound like it is, it seems that whatever gives the most consistent results is the best option. I feel dc fix and plexiglass will work fine for my needs.

Next question (since i have your attention lol) - Do you know where i can find calibrated lights like Maukka was selling?

Yeah, since you will be calibrating the whole sphere as a unit, the exact diffusing sheet you use is not super important as long as it does the job and does not cause anymore tint shift in the light then necessary. Most important thing is the calibration step.

DC fix should work fine, you will just have to play with how many layers to use. I ended up using 3 layers of the diffusion sheet I had to find I would not get any noticeable difference in readings when using different reflectors with the same LED. A sphere is better for this of course but a lot bulkier and expensive.

Maukka is the only source for calibrated lights that I know of, if he has some they are highly recommended.

Thanks TA!