I have an OM to NEX adapter from big_is on eBay that I'm using on my A7. I don't know if it is the adapter or the lens but it seems to vignette on lenses wider than 35mm, wide open and stopped down to f8. No lens hoods were used. The lenses are a Vivitar 28mm f1.9 Series 1 and a Zuiko 28-48mm f4. Has anybody else experienced this with cheap OM adapters or is it just the lenses? Is there a better brand or seller of adapters that I should get?