Sigma HSM 50mm f/1.4

General
I'd heard so many contradictive things about this lens, I had to check one myself. Sharp wide open vs soft; big vs just right; perfect focus vs back focus. What's the truth? Read on

Pros/Cons
+ very fast, excellent for low light or subject isolation
+ very, very good image quality wide open, excellent f/2 - f/11
+ very beautiful bokeh

- slightly more expensive than the competition
- slightly bigger than the competition (for some, it could be a plus though)
- autofocus fast and accurate, but it makes a slight "stop" sound when it locks, which bugs me just a bit

The sharpness of the Sigma 50mm f/1.4 would leave very few photographers unsatisfied

Intended Users
Great for:

• portraits
• street candids
• low light

Not for:

• a general lens - 50mm is somewhat long in DX for general photography
• people with a small camera who want to have a small lens.
• people who can't understand the limitations of working with f/1.4

Final Verdict
A fantastic lens. Forget all the ridiculous diagram-hugging reviews claiming it's soft wide open. It's fine. Of course it's better stopped down to f/2 or f/2.8. But to claim it's not sharp at f/1.4 is simply not true. For real-life photography, this is an excellent lens, with a very beautiful bokeh.

The other claim is that it front/back focuses. Hogwash. I tried two copies and they were both fine. People simply don't understand that at f/1.4 the depth of field is so utterly small that the slightest move (like, when you breathe) can take the subject out of focus. Not to mention if you try to photograph moving children. You need to develop a certain discipline for using f/1.4 - and you need to realize that it requires practice and patience. The autofocus is fast and accurate. Like I mentioned, it does produce a tiny "stop" thud when it locks, but you get used to it.

Some people say it's big and heavy. Well, this is a matter of personal preference. For me, it balances superbly on the D300 - way better than the comparatively tiny 35mm f/1.8.

Compared to the Nikkors (AF & AF-S 50mm f/1.4)
Inevitably, one should compare the three. My take on it: All of these three lenses are great and they can produce fantastic images. Forget diagrams. These are three great, sharp, useful lenses. In a nutshell:

• If money doesn't matter, get the Sigma 50mm f/1.4
  
• If money matters and you have a camera with a focus motor, get the Nikkor AF 50mm f/1.4
  
• If your camera doesn't have a focus motor, you could get the Nikkor AF-S 50mm f/1.4. But the price difference with the Sigma isn't huge - if money really really matters, and you're a DX user, you could consider the Nikkor AF-S 35mm f/1.8. It's a different focal length, though - make sure it's something you can live with