What is the purpose of a lense hood?

Answer 1

It prevents lens flare in bright sunlight, therefore giving a more clear image without those "sunspots"

http://en.wikipedia.org/wiki/Lens_hood

Answer 2

When you point your camera towards the sun, the light can enter and bounce off the lenses inside. This creates a sunflare, which looks like a series of floating octogons in your image.

A lens hood will block the light from coming in from an undesirable angle and avoid the lensflare. However, you have to be careful when you use a lens hood on a wide-angle lens. The lens could actually see the lens hood and you'll get dark corners in your images.

I use a collapsible lens hood made out of rubber and extend it when facing towards the sun. You don't need it 80% of the time.

Answer 3

The lens hood is used to prevent flare. If you are shooting against the sun or there is a strong side light then the lens hood should be used. Else you will get octagonal shapes in the picture.

Also, if a lens hood is attached and the lens falls or it hits some object, then there is some protection as the hood is hit first.

Answer 4

The lens hood is used to keep light from hitting the front lens glass from the sides. Side light on the lens will dilute the contrast and color in your photo. It's a good idea to use one.

Answer 5

It reduces the amount of ambient, indirect light entering the camera--the kind that reduces the picture quality. Most useful when shooting toward or at a narrow angle to the sun. You know how football players put black stuff below their eyes? About the same deal.

Answer 6

It helps keep unwanted light from entering the cameras iris.

Answer 7

to prevent sun flare
http://www.visualparadox.com/images/no-linking-allowed-/palmrow800.jpg
this site has an example of sun flare