I'm planning to buy the Tamron 24-70mm 2.8 VC for my a7s. Majority of 24-70 2.8 lenses have 82mm filter size but I have invested in many 77mm filters. It would be such a pain to replace them. Maybe someone have an similar experience with a step down rings and vignetting. Specially interested in Tamron 24-70 on a full frame camera with a step down ring for 77mm filter. My main filter would be Tiffen Vari ND.