simple note. For Greenscreen work, just use dpx. It's a whole different world to anything else.
We're doing a challenging greenscreen project over here at Allucinari and tried a few options - avoiding dpx because of the file size. Finally we tried it (again) and realized we had wasted all the time not using it. It's not just better on a technical weird numbers level. It's quite obviously visually better.
(Evaluated using After Effects Keylight.)
(Added later for those who might not read the whole thread: tiff and dpx are of similar impressionistic quality, tiff's are larger files thus my preference to dpx. It could be proven that tiff's are technical even better, but the extra 10mb per file has to be taken into consideration for our work-flows. If someone does do tests and it seems to be much better, I'd switch to to tiff.)