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

A lot of interesting answers here. Occurs to me that a person learns to focus the same way that a camera can auto focus. You just look for the focus position that provides the most contrast.