DSLR Lens Primer: Part 1

http://bit.ly/BHCameraLenses
This is Part 1 of a three-part series that lays out the basics of lenses. In this part of the Lens Primer, we explore concepts such as aperture, image stabilization or vibration reduction, and zooms vs. primes.
DSLR Lens Primer: Part 2
http://youtu.be/41Lz0FtVGyo
DSLR Lens Primer: Part 3
http://youtu.be/xqNddEAlzVc