It is not surprising that most recommendations here is for the Pentax lens, If you guys don't mind, allow me to spread some poison for the Sigma 50mm 1.4.
It happened to me again! I was out shopping and happened to walk past my favourite camera shop (not in Singapore). Normally I avoid going in if I have no intention to part with my hard earned cash, But the "End of Year Sale" was plastered all over the shop window. Items on sale included all the latest Pentax gear plus Sigma lenses. The magnet was simply too strong to overcome.
I have read rave reviews about the Sigma 50mm, so I wanted to see first hand how well it really performs. As luck has it, they still have one last Pentax mount unit in stock. So I told my buddy salesman that if it is as sharp wide open at 1.4 as they say in the reviews, I will buy it on the spot. Guess what? I bought it on the spot.
This Sigma 50 is really a beautiful piece of glass. Compared to the FA50, it is large and heavy with a front filter element of 77mm. But in actual use, it sits very comfortably on the palm. I find this is a great for holding the cam steady and helps to effectively manual focus.
I read some comments about the size mismatch with the smaller bodied Pentax but as I always use the battery grip, it is not an issue for me, But even without the grip, it isn't too bad. Pretty much a personal thing I guess.
The HSM AF is great. It is quick and accurate. Will be doing more practical test in the coming days to confirm but so far so good.
I don't own any of the old A & M legacy lenses so I can't compare the sharpness at 1.4 but I am extremely happy with what I see from the Sigma. It simply blows my hooded FA50 away at 1.4. If you are looking for a lens which produces sharp image with creamy bokeh wide open at 1.4, this is the one lens you must consider.
OK, enough words. Here are some pics. All shot in RAW @ f1.4. No sharpening done when resized.
1. Focus is on the EX Sigma logo
2. Focus on the "For SA/KPR"
3. Focus is on his right eye
4. Size of the lens. Takes 77mm filter (Taken with the Tamron 17-50)