OK so I am getting tired of having a smattering of 52mm, 58mm, and 62mm filters. I originally bought 52mm CPLs because all my Nikkor lenses are 52mm. Then I bought my Mamiya and the only lens I have for it is 58mm. I own a yellow and orange filter in 58mm, and I also own a few filters in 62mm that were cheap because a local camera store was closing. So, what size filters should I buy to standardize? Is 72mm too big, or is that a good size to standardize on and buy step-up rings, or should I go bigger or smaller? I plan on sticking with my Nikkor lenses (all of which are 52mm, don't see a big need for new lenses for that system as of current). I do plan on building my Mamiya system from the 80 2.8 I have as of current to a good wide-angle and telephoto lens in the future as funds allow. I "may" eventually move up to 4x5, but that would entail purchasing a new enlarger, so that's a ways off. What about the Cokin system? Is that a good alternative to normal screw-on filters? Thanks!