Check out the Vimeo Video School Series here-
http://vimeo.com/videoschool/lesson/114/behind-the-glass-an-introduction-to-lenses
Part 2: Focal Length – http://vimeo.com/27556331
Part 3: Depth of Field – http://vimeo.com/27556482
Music by digi g’alessio used under Creative Commons:
http://soundcloud.com/digigalessio/morning-jam-with-darth-vader