omni vs. cardioid lavalier mic for documentary

[scorsesefan]

I am starting a documentary and I would like suggestions for omni or cardioid. A great deal of the audio will be sit down interviews. I will be doing the interviewing off camera and probably not miked, but I may throw a few on camera questions the interviewee's way. Any suggestions?
thanks

 

[shawnmaddock]

For body-mounted lavs, I'd stick with omni. It's close enough that the extra rejection of a cardiod shouldn't be critical, and you want to keep your mounting options as versitle as possible, ie. not worrying about how it's pointed.

If I was using a lav as a plant mic and had a cardiod available I'd consider it, but I'd have several omni's in my kit before I'd buy a directional lav.

As a side note, I would re-record any of your own questions that get asked during the interview. Just make sure you're not both taking at the same time, or if you are, ask them to repeat what they just said.