I've been shooting SLRs as a hobby for about 7 years now...first on a Canon Rebel G, and in the past month, I have switched to a Nikon D70. With the Canon, I never bothered to use lens hoods, as I didn't know what they were used for and never really cared to investigate. But since getting the D70 and joining this site, I've become curious. I have the 18-70 D70 kit lens and the Nikkor 70-300 ED lens. So my questions are...what is the purpose of the lens hood? Does it really improve performance, and if so, how? Also, if you do recommend using the hood, should I use it all the time on both lenses, or only under certain conditions? Basically, this is a general, what the heck is a lens hood used for anyway type of question. Any help will be greatly appreciated. Thanks.