Friend of planet5D Juan Pons (Wild Nature Photography) sent in this article he's written on recording audio with your HDSLR.
” I have talked to many folks about how to best record sound when shooting with a Video DSLR, and have experimented quite a bit as well. In this article I will share with you the system that I am now using and which I find is producing great results for me.
Let me first state that if you are serious about your videos, you should be serious about sound; and if you are serious about sound, you should NOT rely on the built-in sound recording capabilities of the current crop (as of Feb, 2010) of video DSLRs. This includes the Canon 5D Mark II, 7D & 1D Mark IV. Please note that I do not have first hand experience with the Nikons, but from what I have been told the situation is similar.”
Please read the entire article!
(Photo credit: snap from Juan's article)