What exactly is the pinhole effect?
To answer the question, let’s start with understanding how our vision works. When light rays enter the eye, the lens of the eye focuses them onto the retina, located in the back of the eye, helping us see clearly. If we had no lens, the light would enter the eye in many places and the unfocused light would result in blurry images. The muscles in the eye change the shape of the lens to focus light at different distances so that we can see up close and far away. For many people, glasses and contact lenses aid in bending the light rays into focus.
If light passes through a tiny hole, or pinhole, all the unfocused rays of light are blocked leaving the focused light to reach the retina undisturbed. The focused light rays help bring images and objects into clear focus. This is the pinhole effect.
Why can I see clearly when I squint?
When we squint, we mimic the effect of looking through a tiny pinhole. We are only allowing a small amount of focused light rays into the eye and preventing the unfocused rays from reaching the retina. Try it. Make a tiny hole with your thumb and forefinger and look through it without glasses. You will find that you can see more clearly. This is the pinhole effect in action and this is why you can see more clearly when you squint.
What else uses the pinhole effect?
If you are a photographer, you probably understand the pinhole effect in different terms like “depth of field.” A photographic lens aperture is used to adjust the amount of light reaching the image sensor. Like a pinhole, the smaller the aperture, the clearer the range of focus.
Izvor:
https://ic8lens.com/the-pinhol...ct-as-a-solution-to-cataracts/