Consider the following two modifications to a camera lens:
Obstructing the about 75% of the lens's front element with an opaque filter as shown here: https://www.youtube.com/watch?v=43W159gPpdQ.
Severely damaging the front element as here: https://www.youtube.com/watch?v=FWzsXeXCwuc
In both cases, the lens continues to produce a complete and sharp image that is free from any obvious distortions or degradation.
My question is: how is it that a camera lens is able to function so well under these circumstances? More precisely,
- why does obstructing the front element in case 1. not result in a significant reduction in the lens' coverage?
- why does damaging the front element as in case 2. not seriously compromise the lens' ability to produce a sharp image on the focal plane?