You can get acceptable results from AVCHD if you shoot properly and have the right tools and time. 4:2:2 is infinitely easier, of course, but if you're like me, sometimes you just have to play with what you're dealt.

I can't recall if your AE version contains Keylight, but it is a great tool for difficult keys if you have it. I know several versions of AE shipped with it. May even be available in demo versions. As videoITguy says, render to an uncompressed format first. Generally I use two stacked instances of Keylight - the first a very hard key to get solid alpha on the subject, and then choke it down to where you have a few pixels removed all around the subject.

You can then use the output of this key as an internal mask on the second instance, so now all you need to worry about is getting good edges. Use the alpha crops in Keylight to remove most of the green around the subject.

I'm not familiar with Boris Red, but if it has the same keyers as Continuum, it can do an OK job if you use the matte choke and refinement tools well. Here are a couple stills from a job I just did. It was such a quickie turnaround I used BCC chroma keyer directly on the AVCHD clips in Vegas, and I think they're acceptable. These were shot with a Nikon 85mm prime on an AF100. A sharp lens makes a big difference. If I used the stock zoom, I would have had many more problems.

www.powerplantonline.com/vegas/Joshcomp.png
www.powerplantonline.com/vegas/Kelleycomp.png

I used a 5D Mark III on a green screen project recently. It turned out surprisingly well. The keys (no pun intended) were: 1) lighting the talent and green screen appropriately (you know this already, having done green screens before); and 2) having BCC's green screen tools. I don't know if Boris Red 3.0 has the same chroma keying filters/fx's as Boris Continuum Complete. If so, you should be in pretty good shape.

I did some testing prior to the shoot with my lighting and camera settings. That helped a lot (see 1). I have a Sony EX1. I do not think it would have turned out as well with the EX1 as it did with the 5D Mark III. But, I did not try it. If you can rent an external recorder to capture the 4:2:2 out of the EX1r, then I would say that would be your preferred setup.

I wouldn't hesitate to do a green screen again, unless I didn't have BCC's toolset.

Sorry that I cannot share my examples - I just don't have the releases to do so.

Thanks atom12,
Lighting and production is not an issue here. My big concern was the color resolution. Your still photos from the AVCHD clips are a nice job... pretty clean keys. Certainly good enough for what I would need given the similar tools I have. We'd all like to use higher bitrate 4:2:2 all the time, but it's not always an option.
Thanks for your input and examples. I think AVCHD will do the job.

Ken

I got a little worried when I saw Kelley's hairdo, and we only had a fifteen minute window to shoot her. I was surprised at how much of her flyaway hair was able to be keyed from an AVCHD clip and Boris Continuum. I think you'll do fine.

Thanks,Jason.
atom12: Yes, my subject is also female...kind of a beauty shoot. I must just be getting paranoid about it in my old age, as in the past I've shot and keyed even DV (using the old "camera on it's side" trick for more apparent resolution to reduce the stairstepping) Keyed with the old Serious Magic Ultra product, it looked surprisingly good.
I'll go with the Canon MarkIII on this one and use Red3.
Thanks to all who helped here.
Ken