Brian is right about the Mamiya 7's being light. I have never tried ND grads with mine. I don't own it, but Mamiya made (maybe still makes) a polarizer that fits on the lens, flips up over the viewfinder for adjustment and then back down for the shot. I think B&H carries them. My memory is that they are pricey (north of $200).
Originally Posted by brian steinberger