Hi, I would like to try Ilfords SFX 200 film with my Mamiya 645. After doing a bit of reading, I thought a Hoya 72 Filter? After setting the camera up for a normal shot with 200 film without the filter, can anybody give me an Idea where to start on how far to stop down to give me a start. Once I have something on negative I think I will be able to work it out from there. Thanks.