- I think the shortest duration your eye can perceive the movement of the shutter would be about 1/30s. I cannot check this at the moment as both my film cameras always contain film! The sound of the shutter also gives a clue; there is a noticeable sound when either a focal plane or leaf shutter opens and closes. Fast shutter speeds would be much faster than blinking.
It’s really difficult to see the whole visual field together; my eyes want to focus on individual parts. Others almost get cut out from my attention. It’s hard to look simultaneously at both a foreground detail and a background like a camera can.