Why does looking through a small gap focus vision so well?

Question

My unaided vision is terrible but if I make a small gap with my thumb and index finger and look through that I can read pretty easily. Why is this?

In: 24

Answer 1

Because you’re making all the incoming light rays pass through a tiny opening, which brings them into focus. It’s the same principle behind a pinhole camera. In theory, the smaller hole you make the more the image will be in focus, though in practice a smaller hole also limits the amount of light that passes through, which also makes the image dimmer.