There are already articles on CPF about different light measurement designs, but none that I found on Integrating Sphere construction. For me, finding a hollow, white sphere was the first challenge. After quite a few searches, a 12" hollow styrene sphere was found at Barnard (phone 888-584-3637). Price with shipping was about $38 - the shipping seemed high until the sphere arrived in a carton almost twice as big as the item.
A top and bottom plate were cut from 1/2" plywood. The sphere measured exactly 12" diameter, and the plywood was cut to 11 7/8" (square) to give the sphere a small amount of compression when assembled.
Four posts (also 11 7/8") were cut to connect the upper & lower plates, and the posts and plates were assembled with yellow glue & brad nails.
The sphere was placed inside the assembly, and four side panels were cut from 1/8" plywood. These are attached with yellow glue & brad nails.
The upper hole is cut with a holesaw to match the diameter of the light meter sensor. The light port is also cut with a holesaw to fit the light tube.
A piece of 2 3/4" stainless tube is used here, but PVC pipe would work just as well. The light tube was coated with Satellite City Special T Super Glue, the inside of the hole was misted with accelerator, and the tube was inserted & twisted until the glue set (about 5 seconds)
Except for applying a finish to the wood, the IS is complete. The light meter is an Extech EA31 (range to 20,000 Lux). It was found on Amazon for under $100 & gives repeatable readings. Since the IS is a comparative device, my concern is that the readings are the same every time a light is retested.
Here are the first Lux readings obtained:
Malkoff M60 in Surefire 6P host - 10,400
Surefire E1B on high setting - 6,540
Surefire U2 on high setting - 6,350
Novatac 120P on high setting - 5,790
Muyshondt Nautilus high setting - 4,900
Surefire L4 - 3,840
Malkoff M60LL in Surefire G2 - 3,330
Surefire E2L (single stage Cree) - 2,970
McGizmo Sundrop - 2,550
Surefire E1L (single stage Cree) - 2,180
Muyshondt CR2 Ion - 1,580
Again, these are comparative readings ... they are not absolute.