I wanted to go back to basics and buy a 50-ish mm lens. As far as I understand the Sigma 50mm Art is not an option because the AF is a real lottery. I'm thinking of the Tamron 45mm SP now, and wondering if anyone had an experience shooting with this lens, especially in terms of AF? How consistent & fast is it? TDP's Bryan C. mentioned he had problems focusing the off-center AF points. I'm not sure if it's just his copy or a common issue. Would love to hear your opinions. Thanks!