Luminance key

Thanks a lot once again Matt. Your knowledge is truly amazing!

One question about the channel shifting thing though - I now remember from the technical appendices of the respective manuals that Primatte, Keylight and the like use various processes on color information (Primatte's use of 3D color space and concentric circles etc.). But I didn't realize that these were not true all-purpose keyers at all in that even if a luma key on a particular channel, after boosting the channel's contrast , would yield a better starting alpha, these keyers will simply ignore that and keep using a standard color-based process only. Is that a limitation of most of these commercial keyers? Of course, as you mentioned, DVMatte Pro does this 3-pass procedure which uses Luma information, but it still uses just one standard process rather than any conditional branching depending on which methods seem to work better with the given footage.

Matt, just to make my objectives clearer - I am part of an indie team in the UK and we don't have the budget to fork out our small VFX work professionally. We manage with self-learning Premiere, AE, Commotion, Maya and so on, sometimes using Brian Maffit's tapes where available, of course your own and sometimes the Meyer's etc. We have a number of shots to plan, where because of the wide field of view required or because the action will require the subjects to move considerably during the action, a properly lit greenscreen of the required size is looking infeasible. Either the quality of the greenscreen has to be quite poor with just ambient lighting or one would have to be comfortable shooting against any uniformly colored background (a white wall say) and be confident that the subjects can be extracted later. Hence, I'm looking into both keyers and roto tools which might help with about 10 mins or so of this type of footage (not at a stretch but scattered throughout the script).

Thanks for the heads up on the SmoothKit plugin. Shall definitely try it.

Tatha