so for a 11-16 tokina. if i want to shoot at 11mm wide with no vignetting , should i get 100mm or 85mm filter ? and can I stack with with my B+w 77mm UV MRC nano filter ?
I won't recommend stacking square filter adaptor with UV ring filter. If they ever get stuck together, you will have a hard time taking them apart.
For Tokina 11-16mm @ 11mm, I would recommend 100mm system. Use Hitech filters & China 100m filter holder & adapter for a cheaper alternative.