I have some questions about Sigma lenses and their compatibility with my PEN EPL1. 1) Does the AF work with Sigma lenses? 2) What is a nice all-purpose Prime Sigma lens for a newbie to M43? 3) What are the major differences between Sigma lenses and the Lumix or Oly lenses? I have the PEN EPL1 and the kit 14-42, and I am looking to expand my capabilities. My budget right now is around $250. I love to take pictures on hikes, and especially rivers and streams, if that makes any difference. Any suggestions and/or wisdom would be appreciated.