why do our eyes (and by extension cameras) have to focus instead off seeing everything in focus all the time?

Question

Why is everything not just always in focus why do our eyes have to focus on certain things while making the forground and background unfocused?

In: 2

Answer 1

For our brains there are two reasons: attention and 3-dimensions

If everything is in focus there are too many things to pay attention to. Your brain isn’t capable of recording everything it sees, so focusing visually helps it focus attention.

Second is that we see in three dimensions. This has two parts.
– The way lenses work, they ‘magnify’ things at a certain distance. That action to make one distance clearer makes another distance less magnified, or out of focus.
– if everything is equally in focus it’s harder for the brain to tell which is in front and which is in back. If those things are still, it’s nearly impossible. Having two eyes helps the most, but focus/non focus helps also.