I just bought a 4/3 (non-m4/3) Oly 9-18 with adapter for a good price. It has a 72mm front filter thread. Can I use a slim 72mm ND filter with the lens (will a slim 72mm ND filter vignette at 9mm, or do I need 77mm)? I would probably buy a single 72mm Haida Slim ND1.8 (64x, 6 stops) ND filter for it, if it does not vignette. Thank you in advance.