j4nu wrote:
I think mechanical should always result in even exposure/vignetting?
Right, that's the idea. But does the reality differ at all from this? I tried some tests this morning with the lens back on. Thinking the non-uniformity I was seeing might be due to light hitting the shutter at angles that would not be possible with a lens in place. That did clean things up quite a bit, but I still see some non-uniformity. Essentially I am using the strobing of the LED to view what the mechanical curtains are doing as they move.
This would only cause visible vignette at high SS like 1/8000 because then the slit separating the curtains is narrow enough for variation in the slit across the frame to be significant. I think it is also related to the question of why is mechanical SS limited at 1/8000, what is the limiting factor? Could be if the slit is 1/2 as wide to get 1/16000, then the non-uniformity becomes for objectionable. Considering how this largely goes unnoticed I think any non-uniformity at 1/8000 mechanical is not very important.
