I'm planning to get Nikon 5100 body only + Sigma 10-20mm + Nikkor 50mm f1.8G.
Thinking this will give me ability to shoot portrait (50mm) and landscape (10-20mm).
1) Does Sigma 10-20mm auto-focus when mounted on a Nikon 5100 body?
2) This will mean I won't have the focal range from 21mm to 49mm and 50mm above. Is it that a bad limitation?