Apologies because I know this gets covered a lot and "fast" and "slow" are relative terms but I'm trying to make a choice between the Pentax 55mm 1.4 and the Sigma 50mm 1.4 and I keep swinging back and forth in my choice.
Most of my photography is low light concerts (guitar bands, not orchestral) and I've moved from fast zooms to fast primes because I like being able to go below f2.8 to get more shutter speed and better isolate subjects against a sometimes busy and unflattering background. I'm using the 35mm f2.4 and the Sigma 85mm 1.4 (love this lens!) at the moment and want to add a 50ish fast prime in the middle. I'm not interested in MF because my eyesight and technique aren't good enough to have to rely solely on that when I've only got 3 songs to get my shots. I'd prefer quiet focus over screw drive so that I can use it in quiet settings occasionally. So I've narrowed it to the Sigma 50 1.4 and the Pentax 55 1.4.
I think I like the Pentax bokeh more than the Sigma and WR would be a nice bonus but not at the expense of missing shots due to slow focus. I figure the throw of the 55mm is pretty long and so slows the focus down but is it a real issue in real life shooting when subjects aren't moving great distances? Is the point to point focus fairly snappy if you're only shifting small distances? I'm also curious how well does the 55mm maintain focus in AF-C mode?
The SLRGear reviews of both lenses claim that a full rack focus and back takes about a second but the general consensus seems to be that the Sigma is faster than the Pentax.
Then there's the question whether the Pentax really worth the extra $300 over the price of the Sigma.
I'm using a K30 so any comments from people using this camera would be most welcome (and comments by non K30 users too of course
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Thanks folks. Been a long time lurker here. It's a great place to wander about.