Here is a blurred version. I blur it so that I can get a sample of average brightness easily.

A - direct light source intensity

B - directly lit white plastic (mostly lit by the bulb)

C - indirectly lit white plastic (not lit by the bulb at all - lit by the B area of the collar)

Measure the ratios of these and then take to the power 2.2 to linearize (convert from sRGB gamma corrected values, to straight ordinary values). This tells us the diffuse value, roughly. (Actually the inverse of diffuse value.) Of course, the C area is partly occluded, and the B area is off-center where the bulb throws some less light than is heading to the camera here. But it is ballpark correct.

I get:

A / B = 9.23

B / C = 9.31

Given the occlusion and also the off-center, these ratios are probably closer to 8. Hmmm - fascinating.

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