Fw-190 Bar.. once and for all...

[heloguy]

The illusion that the sight is changing size is due to the fact that as you move toward, or away from the sight, you're also moving toward or away from the reflector glass, and the wall behind it.

You're actually having more or less surface area of the glass, and wall in your field of view at any given time. The sight stays the same size, the wall and glass change size due to retinal image size projected in the eye.

[IvanK]

That makes sense Heloguy