Originally posted by Rory And beats every prime in the current line-up? Of whom? And what focal length?
Well, let's revisit what I said.
Originally posted by Kirivon Going off center resolution, the Sigma beats nearly every prime in the current lineup.
So...
Sigma 30mm f/1.4 peak center resolution: 2,453LW/PH @ F/4
Pentax 14mm f/2.8 peak center resolution: 2,178.5LW/PH @ F/8
Pentax 15mm f/4 peak center resolution: 2,352LW/PH @ F/5.6
Pentax 20mm f/2.8 peak center resolution: 2,195.5LW/PH @ F/5.6
Pentax 21mm f/3.2 peak center resolution: 2,290.5LW/PH @ F/5.6
Pentax 24mm f/2 peak center resolution: 2,327LW/PH @ F/5.6
Pentax 31mm f/1.8 peak center resolution: 2,345LW/PH @ F/4
Pentax 35mm f/2 peak center resolution: 2,336LW/PH @ F/4
Pentax 35mm f/2.8 peak center resolution: 2,256.5LW/PH @ F/5.6
Pentax 40mm f/2.8 peak center resolution: 2,274LW/PH @ F/5.6
Pentax 43mm f/1.9 peak center resolution: 2,422LW/PH @ F/4
Pentax 50mm f/1.4 peak center resolution: 2,320.5LW/PH @ F/4
Pentax 55mm f/1.4 peak center resolution: 2,318LW/PH @ F/4
Pentax 70mm f/2.4 peak center resolution: 2,238.5LW/PH @ F/5.6
Pentax 35mm f/2.8 peak center resolution: 2,256.5LW/PH @ F/5.6
Pentax 77mm f/1.8 peak center resolution: 2,326LW/PH @ F/4
Pentax 100mm f/2.8 peak center resolution: 2,109.5LW/PH @ F/8
Pentax 100mm f/2.8 peak center resolution: 2,194LW/PH @ F/5.6
Pentax 135mm f/2.5 peak center resolution: 2,130.5LW/PH @ F/5.6
Pentax 200mm f/2.8 peak center resolution: 2,074LW/PH @ F/5.6
Pentax 300mm f/4.5 peak center resolution: 2,082LW/PH @ F/5.6
As for the Sigma 30mm vs 50mm
30 @ f/1.4 = 1,880.5 LW/PH
50 @ f/1.4 = 1,779.5 LW/PH
even up at f/4 with 2,117 LW/PH
And on the pentax side of things
30 @ f/1.4 = 1,850 LW/PH
31 @ f/1.8 = 1,848.5 LW/PH
43 @ f/1.9 = 1,774.5 LW/PH
50 @ f/1.4 = 1,669 LW/PH
55 @ f/1.4 = 1,633 LW/PH
77 @ f/1.8 = 1,932.5 LW/PH
I never once said that the corners weren't soft, or that the sigma was anything other than a specialty lens. I was merely refuting the unfounded assertion that the lens was soft and lacked contrast with personal experience. If we're talking overall performance then obviously the FA31 is leagues better. However, the quality of the DA*16-50 and 50-135 wide open at f/2.8 make the performance of primes at f/2.8 and greater irrelevant to me. I was going to buy the FA31, but I opted for the 30 instead having happened across it by accident on PhotoHito. IMO, the bokeh and overall quality of the sigma wide open is as good or better, plus it's 2/3rds of a stop faster.
Horses for courses. If you want a super fast normal for either low light, maximum separation, or to recapture what a 50 1.4 does on film/ff the Sigma 30mm is hard to beat. If you want an all-around technically perfect lens get the DA40 or FA31. There really isn't anything to argue.