How does the eye know when the image is in focus? There is distance measuring device, only light entering the eye. No outer feedback to be sure that focus is in fact focus not something the eye think is focus.

Question

Thank you all for your respons and upvotes.

I can now see and focus on the answer of my question 🙂

In: 3993

Answer 1

In the once-popular single lens reflex camera the image from the lens was projected onto a ground glass screen. You focused until you saw good edge definition at whatever range the subject was at. As I recall, the brain is good at determining when the eye has good edge definition re: the object I am looking at. If I am looking at something at arm’s length the tree on the horizon is out of focus. The firmware does not appear to be open source, so I dunno how it works.