How does prewashing film affect it? I thought it was merely to remove the anti-halation layer and makes the film more receptive to the developer. I've read in various places how you shouldn't prewash the Ilford FP4/HP5, yet I do and haven't had any problems that I know of. Is doing this wrong? Am I losing contrast because of it? I do pretty much the same 1 min water prewash with all my films.