Anupam Basu , Jul 29, 2005; 12:47 p.m.
Lens hoods are used to prevent flare - stray light getting into the lens which might cause haze and reduce contrast. Important when shooting in situations when you have bright light falling at an angle on the lens surface. Must you use one - no. But you must know which situations might call for one - then even the palm of your hand would do.