Quote Originally Posted by thekingb
If you expect to use the prime in low light situations with ample space, consider the EF 85 f/1.8 instead of the EF 50 f/1.4. The AF is more reliable on the 85, and the 50 is essentially unusable at 1.4 anyway

Unusable might be a little strong. I've gotten plenty of pictures with the 50mm f/1.4 wide open that are satisfactory to me. I own both the 50 1.4 and the 85 1.8, and if I had to keep only one, it would be the 50, especially on a crop body. Keep in mind also that the 50 is much more hand-holdable than the 85.