I think my copy of the FA50 1.4 is usually a bit of a softy till F2.8, then razor like.
But more often than not it seems the AF may be more of the problem at 1.4 or 2.0 for me than the lens being soft.
I have found that I can sometimes get sharper results with MF than with the AF, in light where I might be using F1.4-F2. These are just my observations.
But sometimes it just blows me away... That is what is so frustrating about this lens.
Here is one of my first shots with it. In a dark front lobby at work the day/night I got the lens, and I made my friend pose while I snapped shots. Most were a tad soft but then I would get one like this and....
This is a crop of the original...
And a 100% crop
Model = PENTAX K100D
Exposure Time = 1/30"
F Number = F1.4
Exposure Program = Aperture priority
ISO Speed Ratings = 800
Exposure Bias Value = ±0EV
Flash = Flash did not fire, compulsory flash mode
Focal Length = 50mm
I mean its not glass cutting sharp but for F1.4 in some funky lighting, handheld and ISO 800... If it did this all the time I would never complain about it...
It is truly a LOVE/LIKE relationship... I never hate it, but it does frustrate the jeepers out me sometimes