eli5, how is it that cameras can see clearly underwater whereas human vision gets blurry?
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The himan eye also sees perfectly clear, when wearing goggles. The camera extereior has a glass shield, same like diving goggles and if you remove that glass shield and let the water get into the camera its pictires will come out blurry also.
Whenever light passes from one medium to another, it gets distorted. Going from air to water causes warps and twists to light at the surface. Other mediums do other wierdo stuff.
Our eyes are specialized at handling light as it transitions from air to lens to eyeball. If light passes directly from water to lens, that messes things up. If we wear goggles, that air pocket around our eyes preserves the air-lens-eyeball track that our lenses are good at.
Fish don’t need goggles to see underwater because their lenses are specialized for their environment. They would need water-filled goggles to see in air, though.
Cameras are designed to work in air, and underwater cameras just keep the same design with a built-in goggle-like interface since they need to be waterproof anyway to keep the electronics working.
Our eyes are a wet lens. That lens is designed with a certain amount of water in mind. More water messes with our focus.
A camera is a dry lens, any water is really bad for the lens.
In both cases, you can put a window in front of this lens that protects the lens from the water. This image will be slightly distorted due to water/glass/air refraction (light is wobbly) but be good enough to work with.
The short ELI5 answer is that the camera is wearing goggles. It can see just like a person wearing goggles. The reason things look wonky is because air bends light a little bit, water bends light a lot. Our eyes are made to work with the bending in air. Dolphins have blurry vision in air for the same reason.
how is this question allowed? surely it breaks Rule 2?
It’s how they are built.
The shape of our eyes is not really intended for Ayer, it’s intended for air.
If you look at many creatures in water, their eyes are shaped different than ours; allowing them to see better under water!
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You get a lens when two materials with different indexes of refraction meet along a curved surface. For the human eye (or any land animal’s eye), the two materials are air, and whatever the eye is made of (mostly water). For a camera, that’s glass and air, plus more glass and air inside the lens because a camera lens almost always contains multiple pieces of glass.
Put a curved eye under water, the index of refraction is all wrong for what the eye evolved to handle, and you’ll never get it to focus.
Creatures that live under water evolved eyes that work when in contact with water. I presume a fish would be just as blind when pulled up into the air.
You can avoid the whole problem by having the interface between the eye and the outside environment be completely flat. Light passes through an interface like that without bending. Put the actual lens parts behind the flat surface.
This is why you can see clearly into an aquarium, or through swim goggles or a scuba mask. Underwater cameras are either placed in waterproof cases with a flat piece of glass for the camera to look through, or if the camera is truly waterproof like a [Nikonos](https://en.wikipedia.org/wiki/Nikonos), the front surface of the lens will always be flat so that the camera works both in and out of the water.
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