Most cameras save a highly compressed file to SD or Compact Flash media cards. One option that is available on higher end cameras is the ability to capture from a clean HDMI signal so that you can use an external recorder to save your video into a higher quality file format.
Originally the Canon 5D Mark III lacked the ability to capture clean video from it's HDMI output. Over at NAB 2013, I was able to check out a few companies who were already testing the firmware upgrade. One booth was Convergent Design displaying it with a new Odyssey 7/7Q monitor, and the other was at the Atomos Ninja booth.
Canon 5D Mark III with Odyssey 7 / 7 Q OLED Display + Recorder
Hopefully we'll see this firmware release very soon and with this unlocked feature that adds a new option to capture from the HDMI output of the Canon 5D Mark III (making the camera better than it already is), I'm sure this will drive further demand to this camera body. Most places right now are listing the Canon 5D Mark III for $3300 dollars, but you will often find ebay Deals on the Canon 5D Mark III listing for $2899. Might be worth taking a look (click here).
Canon 5D Mark III (Body Only)