eli5 Why do camera lenses need to focus on something? Why can’t they just render an image in which everything is clear?

Question

Or maybe only some types of lenses work like that?

In: 281

Answer 1

There are several good answers but I want to make a literal eli5.

All lenses have to focus on something, even your own eye. Try this , hold your finger about 15 centimeters ( about 1 banana’s length if you’re American) from your eyes. Close one eye and look at the finger. You can see yhe grooves on your finger and everything else looks blurry but if you look at something farther while still holding the finger at the same place, the finger becomes blurry.

That’s just how seeing works.