I am reading a lot on Blf because i want to build my own Lumen Sphere / Tube.
In the last few month i see more and more Tube versions instead of Spheres.
Apart from the size (the tube version would take less space to store) what are the pros and cons from Lumen Spheres vs Tubes?
If you’re talking about an integrated sphere it would be price.
A tube can be smaller, has an attractive and easy to understand geometry (light goes in at one end, measurement comes out the other end) and it does not roll over. And it is good enough for what we do on BLF: measuring light flux of flashlights which in general have similar beams.
For good integration that can measure the total light flux of any light profile, the device of choice (for over a century) is an integrating sphere. It requires building carefully but then your measurement error can be made smaller than the tube-style device.
Thanks guys!
I asked because the 40cm sphere is taking a lot of space (if you see it in real its bigger than expected). And when its ready i would have to build a box arround it for protection.
The Tube design would not need so much space. And no need for a huge box to protect it.
Mhhh will have to think about it.
Subscribed to this one. As of right now I don’t really have the space to set up either option but, hopefully in the next few years that will change. When I bought this house I didn’t think I would get back into any of my former interest again. Now that I am, I could really use a dedicated space. Right now my work/radio/knife/light/electronics shop fits in boxes that I have to drag out, set up, complete work, and return all the materials to said boxes again. Makes a 5 minute job take an hour or more sometimes. Now I have to save a bunch of projects to do at the same time so it’s enjoyable instead of feeling like a job.
Looking forward to doing some more reading on spheres and tubes.
Been there, done that, got a few Tee shirts & empty wallet to prove it. :money_mouth_face: . 
You need to consider what size and power of lights you intend to measure.
I’ve got a Josh K sphere and it’s 12 inches in diameter. Due to its small size you’re limited to the size of the opening you can have for the flashlight. On mine it’s about 1.5 inches and the upper lumen limit is around 1000 lumen. You can increase the lumen handling by adding a neutral density filter over your Lux meter sensor. This reduces output by several factors and can allow several thousands of lumen to be measured. You’re still limited by the size of the opening, though. You can’t just cut a bigger hole in the side of it because then you lose the ratio of interior surface area to the inlet port which will cause problems in your measurements.
For a large head light or several thousand lumens you need to go to a pretty large diameter sphere like maybe 20 inch, but of course that takes up a lot more space.
The tube-style integrating spheres can handle a wide range of head sizes depending on the diameter of pipe used. They can also handle very high lumen outputs plus are much more compact. They may also be cheaper and easier to build.
When you get up to really big lumens, like 30k+, I don’t know how the tube style will respond. This is where you might need a beach ball sized sphere.