it's a special effect used in motion picture film.....although I've never done it--I think it would be pretty easy with 6 step E6, if you did it by hand or had someway to bypass the step on a processor. I don't know about setting up the rest of the process or adjusting the film speeds though--I read a little bit about this a couple of years ago on PDN's site, you could check there....my impression was it's similar in a way to cross processing.hope this helps a bit.