On Dimitrov's site both the K and the A are referencing the same diagram, there might be improvement in lens coating over time though, but I am not sure.
As has been said it is the K version. It's not known if Pentax changed the coating formula between the K and A but many believe so. IIRC the A has nine aperture blades versus the eight blades of the A.
I don't know if the lens is famous or not. I have owned two copies of the A version and it was a nice fast 50mm. Just as so many Pentax lenses the LoCA is there, or very much there. The glow at wide open is quite pronounced. When compared to the SMC-P A50/1.4 and SMC-P A50/1.7 the f1/2 lens is "sharper" at the corresponding aperture values. Bokeh is very personal so you've better judge that yourself.
Above: Some sort of flower, wide open at close distance and then somewhat cropped, taken 2006 with a Pentax ist DS (an 1.5 crop 6MP camera)
From all discussions about this lens at different Pentax forums I don't think the difference between the K and A versions is anything to really care about.
Jonas B wrote:
From all discussions about this lens at different Pentax forums I don't think the difference between the K and A versions is anything to really care about.
Indeed. I would not worry about the difference (if any) between the two.
Paul: if by "famous" you mean the Pentax that was tested in that German test of the sharpest 50 1.2, then it is the K version. Obviously, in that test, they did not test any of the M Nocti or the Contax Jahre.
nixland wrote:
I have both the K and A. The A is signifantly much sharper than the K, but the K has smoother bokeh.
This inverse relationship seems to extend across other brands, generally. The sharper ultra-fast 50s are generally sharper due to over-corrected spherical aberration, which results in edgier, sometimes "nervous", sometimes plain "ugly", bokeh (ie. not smooth, and yes I realize bokeh beauty is subjective).
The rules change when the lens design creeps away from the 50mm mark, which is why we have several examples of fast 55-58mm lenses which strike such a good balance between sharpness and smooth bokeh. Porst 55/1.2, Contax 55/1.2 100 Jahre, Canon FL 55/1.2, Noct-Nikkor 58/1.2, Rokkor 58/1.2, Konica Hexanon 57/1.2, etc. etc.
Some might argue that they like the "sharp 50mm bokeh" better. Granted, people have different taste. I am merely making the observation that it is difficult to find a sharp 50 with creamy bokeh, and much easier to find a sharp 55-58 with creamy bokeh, regardless of manufacturer.
The Zeiss lovers might just ask themselves why Zeiss strayed away from 50mm for the 100 Jahre f1.2; I think it is obvious if you compare the 55/1.2 bokeh to the two Contax 50s.
Minolta, Canon and Nikon users can make the same comparisons between the respective 50s and the "slightly-longer-than-50" lenses. The trend applies seemingly universally.
cogitech wrote:
This inverse relationship seems to extend across other brands, generally. The sharper ultra-fast 50s are generally sharper due to over-corrected spherical aberration, which results in edgier, sometimes "nervous", sometimes plain "ugly", bokeh (ie. not smooth, and yes I realize bokeh beauty is subjective).
Yes, I think the same about the over corrected sa. Same thing happened with my Samyang 85/1.4, the first version vs the UMC version. Exactly like the above K vs A comparison .. smoother bokeh vs sharper images
cogitech wrote:
The rules change when the lens design creeps away from the 50mm mark, which is why we have several examples of fast 55-58mm lenses which strike such a good balance between sharpness and smooth bokeh. Porst 55/1.2, Contax 55/1.2 100 Jahre, Canon FL 55/1.2, Noct-Nikkor 58/1.2, Rokkor 58/1.2, Konica Hexanon 57/1.2, etc. etc.
Some might argue that they like the "sharp 50mm bokeh" better. Granted, people have different taste. I am merely making the observation that it is difficult to find a sharp 50 with creamy bokeh, and much easier to find a sharp 55-58 with creamy bokeh, regardless of manufacturer.
The Zeiss lovers might just ask themselves why Zeiss strayed away from 50mm for the 100 Jahre f1.2; I think it is obvious if you compare the 55/1.2 bokeh to the two Contax 50s.
Minolta, Canon and Nikon users can make the same comparisons between the respective 50s and the "slightly-longer-than-50" lenses. The trend applies seemingly universally.
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An interesting theory. I have the Jahre myself, and I wouldn't call its bokeh "creamy". Longer FL compresses the scene more so it might appear to be smoother. In the list of your 55-58, I have tried all but the Noct Nik, and the Jahre definitely has better SA correction (less haze/glow) than all of them. So I think, like you said, it might simply be how much they decide to correct for the SA.
hiepphotog wrote:
An interesting theory. I have the Jahre myself, and I wouldn't call its bokeh "creamy". Longer FL compresses the scene more so it might appear to be smoother. In the list of your 55-58, I have tried all but the Noct Nik, and the Jahre definitely has better SA correction (less haze/glow) than all of them. So I think, like you said, it might simply be how much they decide to correct for the SA.
Regarding focal length, my point is that I suspect it is easier to achieve a better sharpness vs. creamy bokeh (or at least "creamier") balance at the slightly longer focal lengths of 55-58mm. The Jahre bokeh may not be "creamy" but it certainly seems"creamier' than the 50/1.4 or 50/1.7 (all things being equal except focal length) and I suspect this is why Zeiss chose not to make it a true 50.
Is it just the compression which provides this bokeh "advantage" (again, subjective I know) or is there something else at play? I don't know, but I suspect there is; the focal length difference seems quite small to me in relative terms. When we jump to 85mm, certainly it is a whole different playing field but from 50 to 55, 57, 58?
Sorry to derail the thread, but it seemed as though the original question was answered quite well. I'm just thinking aloud here...
