Lumen tube considerations

Off-topic Chatter
1

Hi flashlight fanatics!

I have freezer type integrating device to measure approximate lumens of flashlights. Disadvantages are that I can measure up to about 6k lumens in that box. So I want to make another one. What do you think would be more accurate lumen tube from PVC pipes or to make integrating sphere out of glue and newspaper or fiber glass?

2

If your goal is to measure lights with over 6000Lm, try to add a baffle or filter over the sensor and find out the correction factor using other known lights

3

My first goal is to make measurements as much accurate as possible, and then to be able to measure above 6k lumens.

4

The sphere should be more accurate. Problem with pipes is that direct light will see lesser reflections and so is overweighted. I.e. a thrower appears to have more lumens than a floodlight.

5

That was the thing I worried about. So then maybe anyone has any links how to make the sphere and where to put measurement device and baffles in it?

6

A sphere is the way the pros do it. But it needs to be large to deal with a large powerful light.
Tubes are more compact and, with the right amount of fiddling, seem to be the method of choice lately.
Depending on the design, there is often a difference between the measurements for throwers vs floods of the same Lumen output.
This can be mitigated by careful use of diffuses and tube lining.

There are several threads about DYI Tubes, boxes, Etc.
The key to all builds is to have a known standard to calibrate the measuring device against.

Maukka sells calibrated lights. But they are low powered.
His thread with several builds:

Texas Ace Calibrated Lumen Tube:. Widely used by many in the BLF and other forums.

My DYI Adjustable calibration Lumen Tube

And a few more from djozz

And others

A short thread discussion about a high powered reference and the linearity of the measuring devices.

There are many more. It would take a bit of searching to root them all out.
All the Best,
Jeff

7

The sphere is the most accurate, and a Maukka calibration light is a must.

I built one myself, the most disappointing thing was that none of my lights reached their claimed Lumen output.

When you have more questions, just feel free to ask.

8

Thanks for all the links. Maybe you can inform me where to buy maukka light?

9

A simple idea to measure mucho lumens: Take a measurement of a lower power mode, then measure lux. Now measure lux of max power mode and apply ratio.

L_turbo = lux_turbo * L_low / lux_low

10

It’s the first thread I listed

I’m not sure if he’s still offering them.

The second thread from Texas ace is where he was selling calibrated lumen tubes.

Djozz builds show some adventures with spheres.
All the Best
Jeff

11

I couldn’t find anyone here selling the calibration lights anymore, I’d like to get one, I have the T/A tube.

12

Yes, I just noticed that Maukka is not selling them anymore. I’m only a year out of date.
Sorry for the false hope…
I’m not sure if this is a permanent thing. Hope not.
They are used by many as well as the Texas Ace Lumen tube.

You might put a post wanting to buy calibrated lights in the
https://budgetlightforum.com/forum/marketplace/buy

Forum and see if anybody has a set they want to sell.
All the Best,
Jeff

13

I’ve never seen more lumens with my PVC tube over a Sphere that others have. If both are calibrated with Maukka lights, my tube is always less no matter what light is used.