Slightly different spin than most comparisons of these two.
I've currently got the 50 f/1.8, but decided to "bump up" to something with slightly better build quality. Knowing that there's a significant difference in focal length, here's my current dilemma:
I ordered the 50 f/1.4, but the place I ordered from is now out-of-stock, so I am now second-guessing if I should switch to the 85 f/1.8. I have no doubts that eventually I'll own both, but my primary need is low-light. I've got the 85mm range covered with my 70-200 f/2.8 (although 1 1/3 stops slower than the 80/1.8 ) and my 24-105 f/4L with a 580EX II does well with overlap and my "all purpose" lens.
However, there's a lot of times I need to take a non-flash picture.
f/1.4 versus f/1.8 is 2/3rds of a stop (not insignificant). I know the math, but has anyone run into the practical applications of f/1.4 where you knew that f/1.8 just wouldn't cut it?
I know I've had the same case with my 70-200mm... I've shot at 200mm, f/2.8, ISO 3200, at 1/30" and gotten a clear shot... Anyone shoot the 50/1.4 and knew nothing else would have made it?
Convince me to not change my order.