What Does a Lens Hood Do?

A 300mm DSLR lens placed on a stump with a round lens hood attached.

Everytime I see one of my photography students with the lens hood on backwards, I know they don’t know what the lens hood does. ┬áThe lens hood is designed to reduce flare and protect the lens, among other things. What is the purpose of a lens hood? The lens hood is a piece of plastic CONTINUE