I'm going to shoot some kids jumping in front of a green screen (SDX900). I will probably slow it in post using Apple Motion's New Optical Flow Retiming tool. I like to shoot 24p for the look, but I realize it all ends up interlaced in FCP anyway. So my question is... Should I go to 30p or 60i? Also, I figure I should add 1/100 or 1/120 Shutter. I want to get as much info to Motion for the retiming. Is there another setting (Tape Mode/Setting) I should consider for the recording?
60i would give you the maximum motion samples for post-production slow-motion. You could then deinterlaced for that 24p look. That said, for the price of the good filters you'd need to get solid slowmotion and 24p, you could easily just rent an HVX200 and shoot 60fps. It should match very well to your SDX900.