edit: I posted my lazy solution. It probably isn't that great. You should probably find something unique and not just something I thought up in a minute.
My box look rather like yours. I used a bit of translucent plastic cut from a milk container to act as a diffuser and to prevent dirt from getting in the top hole.
I put in a barrier in the middle so that no light can go directly from the torch to the meter, it has to bounce around a bit first. Think of it like the letter "T". this hangs from the top of the box.My meter's sensor is held in place with the extremely high tech approach of duct tape. I have put cardboard flaps over the input and meter ports to keep light and dirt out.
All you need to do is work out the light output on several of your lights : [ Driver efficiency ] vF cF , type of emitter , and your good to go after some math ...
That's a pretty good idea, but be sure to crinkle it up first to reduce directionality.
If you have a laser, you can use it to test the effectiveness of your contraption as well as troubleshoot consistency. Readings shouldn't change with it pointed to different angles at the input.
With my lux meter on the way... im going to make one of these.
Since i would love to have cosistent readings what's the best way to design the "integrating sphere"?
The sensor of the light meter should not allow other light to go inside. (poorly made hole).
The internals should be made of non reflective material. What would be best? Lined with a old cotton shirt?
The aperture for the flashlight should probably have the antique photo camera rug installed so no other light can pollute the internals?
Shape? Sphere seems logical, but is really that disruptive going for a square box? A dodecahedron would be batter than a box?
A cheap plastic ball might be just the thing. Cut in half, and then heavily brushed to kill any reflectivity. Glued together and glued/ in a wood cage to preserve shape...
If i understood correctly i win if i get my measurements cosistent, but i will never be able to know if my calculeted lumen output of 320 in reality can be 304 or 330?
Being lazy and hating the maths led me to set mine lightbox to direct reading in Lumen.
Calibrate it with the ITP A3 the only 'trusted' stock not touched I own as 85 lumen in high 23 in med...given the readings I get probably the actual output in mine is 80...
RC-G2 with XR-E R2 at 1,4 A 340 Lumen
RC-G2 with XP-G R4 at 1,4 A 408 lumen
RC-G2 stock XR-E with rechargable cell 130 Lumen
MTE F15 P7D at 2,4A 620 Lumen
P10 with XP-G R5 at 1,4 A 470 lumen
I think all the number are too high maybe 10% or a bit less
I need to work in the reflection issue because the throwers perform way better than the flooders or candle mode...