Here is the prop rendered.

The first rectangle is colored 255, i.e. 1.0 in unit-range.

This is to be expected. It is facing the light.

N dot L = 1
Therefore, the reflected light is 1.0, 1.0, 1.0

2 is 15 degrees off. The cosine of 15 degrees is about .9659. Converting to 8-bit, I should find the rectangle colored .9659 * 255 = 246. It is.

#3 is 30 degrees off. The cosine of 30 degrees is about .866. Converting to 8-bit, I should find the rectangle colors .866 * 255 = 221. It is actually 221.

Wow - math.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)