10-2023 - I can still build lumen tubes to order
Prices for the tubes would be:
$185 + shipping for the 3.5”
$300 + shipping for the 4.5”
Ok, I have had several people ask me if I can make them a lumen Tube / Sphere like mine in recent times. My first sphere was simply too much work (literally months to get it calibrated) to make this possible.
Then the other day when testing some 20k+ lumen flashlights. I noticed that my sphere was starting to melt slightly.
So I decided I needed to make a replacement while this one still worked as a standard to calibrate the new one from. I had also been thinking of improvements for some time and finally got my hands on the right materials and tools to make this possible.
And thus, the Texas Ace integrating Lumen Tube was born!
It uses all the same principles from my earlier thread on lumen spheres
The only real change is in the diffuser. Instead of foam this time I am using some laser cut diffusing sheets that fit perfectly inside the PVC pipe. This makes it much more consistent and repeatable. Interestingly the direction you insert the sheets has a noticeable effect on the readings.
I also put another sheet between the 2nd PVC connection to further spread out the beam to remove any bias for throwers or other lights that these type of spheres can have issues with. The end result is a perfectly smooth wall of light hitting the meter. I fine tune the readings with magic
The best part of all about this sphere is that unlike every other sphere I have ever seen, the lumens will be displayed directly on the meter!
You will not have to run the lux meter readings through one or more calculations just to see what the lumen reading is, you simply stick the light in there and read the lumen directly on the meter. When I am taking dozens or even hundreds of readings a day this is a lifesaver.
In this picture the light is putting out 193 lumens, this same light and mode reads around 195-196 on my old sphere for reference. I can get that closer but have just not had the time with all the mt09R mods and frankly don’t care since I only give it a ~10% accuracy rating anyways.
So I am planning on making a 1 time batch of these spheres. They will all be calibrated by me with my sphere so the readings will be comparable.
These spheres will come with everything in the pictures
The PVC tube itself, able to fit up to ~89mm reflector lights
HS1010A Lux meter like mine
a range of centering rings for different size lights
calibrated to match my sphere within ~5-10% or so (to give some wiggle room since it is impossible to get things perfect)
I have tested this sphere with lights up to 25,000 lumens and it should in theory be able to read well over 100,000 lumens if the light would fit in the tube, although you would have to worry about melting something at that power level.
Ask anyone that has tried to calibrate a sphere from scratch, it is way harder then it sounds. My sphere took me 6+ months and countless lumen readings before I was happy with the readings.
The lumen tube is far from my idea, The credit for the basic lumen tube setup belongs with BLF members from long before my time.
Making it an “integrating lumen tube” by adding the diffusing sheets and the centering rings to make the readings more consistent light to light was simply my evolution of the idea.
The addition of diffusing disks inside the tube also vastly improve the consistency from light to light and removes the advantage that throwers have classically had in PVC light meters.
Thanks to JasonWW for the illustration.