Most of the information I have I accumulated by reading message boards, and just picking bits of info here and there, so I easily could be totally wrong with everything I am posting here.

From what I understand though, HDV uses 4:2:0 color sampling, which is the same amount of chroma information per pixel as DV's 4:1:1 (ntsc) just laid out in a slightly different pattern.

However, since with HDV you have more pixels to begin with, it seems to me it should be possible to downrez to HD and retain more color information than if you shot with DV, which seems should work better for chroma keying and color correction. So if I downrez 720p HD, what kind of chroma sampling does that give me in SD? Or do you loose that extra chroma detail in the downrezzing process?

I did a quick search on "4.2.2" and found this thread: http://www.dvinfo.net/conf/showthread.php?t=75667

There are other discussions on this topic here too, though - look around...

Theoretically, you could downrez 4:2:0 or 4:1:1 to 4:2:2, and in effect not downrez the chroma as much as the mono. I would do my effects first, then downrez. Best to test with the equipment you're using.