Apparently, the current ISO 800 color films can be pushed several stops and look ok at EI 6400 when push processed several stops. But what happens once the 800 speed films are discontinued? ISO 400 will be the fastest for color film. I can't imagine how one would get a working EI 6400 out of an ISO 400 film. You'd have to push process it about 6 stops. I wonder if it could tolerate that. Also, how long do we have until ISO 400 is the fastest color film available? I'm guessing that 800Z (which was almost discontinued and there are now rumors about being discontinued in 120) and Portra 800 won't be available too much longer. We may be down to Ektar 100, Portra 160 NC/VC, 400 NC/VC, Fuji Reala 100, 160S, 160C, and 400H for color neg film in the near future. Maybe Porta 400NC in 120 or 220, rated at EI 6400, and custom pushed (in a Jobo) about 6 or 7 stops will be the answer. Yeah, that's crazy. I wonder how it would even work. Maybe digital will be the only way to shoot in low light in several years. Seriously, we need a solution so we're not kicked on our butt when they discontinue the 800 ISO film. Seems like higher ISO color film is a shrinking market.