When filming exteriors, are there dirt issues to worry about on lens due to higher f-stop? I know this can be the case with HD video cameras, especially if facing anywhere near the sun. This is why I roll in ND with my video camera to open up iris. If same applies to DSLR's, are neutral density filters the answer, or would polarizing filter even be a better option? If ND, can anyone recommend which neutral density (.3, .6, .9) to get for bright exteriors? Thanks.

Hey Steve good to see you on here.
You are exactly right on n regards to dirt on the lens.

In order to correct this you either have to make sure that your lens is clean (duh moment) or use a filter to help minimize. And the ND filter will be your best choice.

One of the better ND filter that I have seen is one from FilterND
FaderND - FaderND Ultra - Products (http://www.faderfilters.com/products.html)

In one ND filter you get 2-8 stops of ND, pretty cool and convenient.

BTW, I didn't know that you picked up and 550D also. I got mine a couple weeks ago, love it.

I'm bringing it to the filmfest next week. See you there I guess.