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03-13-2010, 05:36 PM   #1
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Pentax 50mm f1.2

I know this has probably been asked about a million times, but is there any difference optically between the Pentax "A" 50/1.2 and the Pentax "k" 50/1.2? Can I assume that wide open they perform the same?
A lot has been made of the "A" version of this lens recently. Many people say that wide open it is sharper than anything else out there at f1.2 in the 50-60mm range. This would include the Minolta 58mm Rokkor, Nikon Noctilux, etc. Anyone care to jump in on this?
I have found most other manufacturer's f1.2's that I have tried out to be soft, and with a lot of flare and CA. I am hoping to find a normal lens that I don't need to stop down to f2 to have decent sharpness. Probably it all comes down to sample variation anyway...

03-13-2010, 05:57 PM   #2
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It's listed as identical in construction here

As for sharp wide open, it is very sharp to almost a pin point. At 1.2 the lens has only a few millimeters of in focus focal range. But the bokeh with this lens is beautiful. That being said, if you don't plan on shooting that wide a lot, you'll get very close results from a 50mm f1.4 wide open. The in focus area will be a little greater but it still renders a very nice image with good bokeh. IMO the SMC Takumar 50mm f1.4 is sharper than the 1.2 when shot wide open from what I saw with both lenses.

One of our members here put hours into a test of 50mm's : 50mm shootout

When it all was determined, the SMC Takumar 50mm f1.4 came in a close second to the A SMC 50mm f1.2. I've owned both, agree with the findings and have kept the Takumar. Beautiful lens.
03-13-2010, 06:56 PM   #3
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The A version has one more aperture blade. Wide open, that isn't going to matter. It doesn't add any real information to the discussion. Sorry, I can't help it.

The only f1.2 lens that I've used is the Cosina 55mm f1.2. I wouldn't describe it as sharp wide open, but when I use it, that's not what I'm looking for anyway.
03-13-2010, 06:58 PM   #4
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The A lens has A capability, of course, which makes it easier to use on a digital body.

03-13-2010, 07:48 PM   #5
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To a degree. The advantage of an M42 lens over a K or M mount lens is being able to use Av mode. Once you get used to the exposure comp needed for the lens, you can shoot much like an A series. Sure it might not be quite as fast to change settings but at 1/5th the cost and fairly similar results, I can live with that.
03-13-2010, 07:53 PM   #6
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The M, A and F 50mm/1.7 are all pretty sharp wide open. Sharper than the 1.4 versions, I think, and maybe the 1.2s.

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