I've read that when you plan to cross-process film you need to overexpose it by about one to three stops. I'd like to do some cross-processing with Provia 100F and Velvia. How much should I overexpose for each (I don't mind a bright, washed-out look for this)? Thanks!
That is far from a hard and fast rule. I cross Ektachrome 100VS at the rated speed and it works very well.
I did this once with Velvia (4x5), but it was about two stops underexposed after the cross-processing.
I was just at lomo.us and someone posted some very nice xp stuff. He said that he just used the rated speed. They might be a bit hot but it's hard to tell from the prints. XP always looks pretty contrasty.
Provia 100, rated at 80; processed normal; no filtration when shot
I xprocess a lot and rate the film as follows:
velvia 40; provia 80; (30cc mag filter and associated 1 stop slower is helpful for these films)
Overexposure and pull processing can work if the film is fresh otherwise the film realy blocks up if you just over expose. Older film that has lost a stop or so of Dmax is were I think this rumor started. Velvia, Provia, E100s/sw/vs are so contrasty when xprocessed that they can become unprintable. But if those same films are older where the Dmax has slipped, then you can 'hammer' the film with light, get great saturation interesting crossover and a printable neg.