Great, I'm looking to use all my lenses with a step-down ring to 49mm for filters and further step-down rings to make compact lens hoods as far as the lenses allow without vignetting.
Originally posted by jatrax OK, you got me curious. I often use CPL plus ND when shooting waterfalls, but never with 40mm that I remember. So here is a test shot with lens + CPL + 3 UV filters + hood. There might be a bit of vignetting, or not, I am not 100% sure but it is not much if any. And that is with a total of 4 filters stacked, CPL plus three UV. So I think you will be just fine with CPL and ND.
Thanks, that's good to hear.