Dan, slide film is much more amenable to over- and under-exposing and having it push- or pull- processed than print film. It doesn't work that well at all with print film. Most, if not all, of the time when print film is processed, the machine makes corrections for over- or under-exposure which is why bracketing is of less use with print film than slide film.
Agreed with the assessment of not pushing print film. Why bother, although I have on occasion pushed Fuji 800 to 1600.
The reason that you don't routinely push slide film is that when you do, there is always some loss in quality, generally manifesting itself as additional contrast or grain or both. On occasion, colors change as well.
That said, some films push wonderfully. Fuji Provia f100 works outstandingly well pushed one or two stops. So does Provia 400. Many pros push Velvia a stop, but I always felt that was in emergencies only; to my eye, the contrast gets too intense when Velvia is pushed.
Kodak E200 tells you that they recommend pushing it a stop and Fuji used to make a film called ms100 that was designed to be shot at anywhere between 100 and 1000 iso. The introduction of the Provia 100 and 400F films spelled the demise of the MS film. Provia is better.
So - don't push slide film unless you have to, but if you shoot Provia 100F or 400F don't think twice about it. Incidentally, I expose Provia 100 @ 160 and Provia 400 at 640 and tell the lab to give it a one stop push. Seems to work quite well. If I push Kodak E200, I rate it at a true 400 for a one stop push.
Keep in mind that a ''push'means the entire roll, so better stick to similar subjects on that roll.
I see references to pushing in articles published in PP, e.g. Bob Krist and others. I suppose it's OK if need be, and I'm sure Bob knows what he's doing, especially if he can write a good article on the Calif. coast!
For my own pennies, I still stick to the idea of using the slowest film I can get by with. That usually means ISO 100, and if I need faster, as for telephoto shots, OK. I used an awful lot of 64 speed film it its day. I've been told the original Kodachrome was something like 6, yeah SIX. Guess we've come quite a ways!!
It's not the camera, stupid, it's the EYE. [IMG]/ibb/skins/default/emoticons/eek.gif[/IMG]
I am not particularly crazy about VS100 pushed one stop, let alone 2 stops. I mean it works, but the contrast gets a little hard to take.
But you know what - why take his or my word for it. Try a roll and see what you get and how you like it. But, if you want 400 speed slide film, use ProviaF400 - I guarantee you will like the results better than 100VS pushed +2. Well, then again, maybe not.
Can slide film be push-processed as successfully as print film? Any reason I shouldn't shoot Kodak Ektachrome E100VS as 200 ISO and have it pushed?
There is a fallacy in your question. Consumer color negative films cannot be push processed because normal processing reduces all of the exposed silver halide in the latent image to metallic silver prior to redevelopment to create the dye clouds that form the negative image. There is nothing left for the chemicals to act on during the extended period in the developer. Only a few professional market color negative films designed for use by photojournalists can be push processed.
That said, transparency films can be push processed to compensate for underexposure. There is no reason why you couldn't shoot E100VS at EI 200, but there's no reason to do so under normal conditions. Push processing is usually reserved as a last resort when the light is too low to expose the film you have with you. Under low light conditions it is better to use an ISO 400 or 800 film than it is to push an ISO 100 film. The extended development will result in increased grain and contrast that might not be too desirable. The underexposure will also result in a color shift or loss of shadow detail that could also be objectionable.