I have one for all sizes of lenses I have. I like these better than the hard hoods that come with some of my lenses, also some lenses do not come with a hood. When fold back when left on the lens will function as a soft rest for the lens when you set your camera down on a hard surfce. I do not rely on hoods for protection (as some will claim about the hard hoods) so these soft ones work well. One word of caution would be to watch for vignetting when these soft hoods are added to the end of a few filters. That is not enough to not use them.

Lucky you! I found an article in LA Times Sunday 1/8/2012 which was about the great classes you can take in Yosemite, CA National Forrest. Some are free & some for a fee & they all sound great.
Anyhow, your looking for "Hstogram information" the gentleman sharing his experience actually added a link which teaches the histogram. Well here goes & I hope it helps. It's a long one too!
Www.ehow.com/how_4523400_use-histogram-photography.html this is better know as the "ehow website" I've never heard of but do look forward to checking it all out.