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

With enough light, and a narrow-enough aperture, lenses can focus on almost everything at once.

Explaining this simply requires simple diagrams and practical demonstrations that unfortunately cannot be easily described. Look up “depth of field” and “aperture” for the simple diagrams.