My understanding is that if you're final destination is only for a film out or DVD out thru a progressive scan deck, you can gain benefit from the added vertical information in the resolution of the image, but if it has to be converted into NTSC (in other words, to a tape-based format), with the lower resolution of 525 scan lines, the extra verftical resolution causes unwanted aliasing and jitter. In that instance you would want to set v. resolution to interlace.