Which 50mm 1.4

I need (want!!) a good standard lens for low light and studio portraits.
It appears my choice is between the Pentax FA 50/1.4 and the new Sigma 50/1.4.

From reading this and other forums it appears that they both give excellent quality, but the Sigma will be better at focussing in low light (especialy in the studio under modelling lights) and is obviously quieter because of the SDM. However the Sigma is rather more expensive - maybe getting even more expensive in the near future.

Unfortunately its unlikely anybody has both lenses so could give a comparative view, but I would welcome peoples views/comments.

I currently use the 50-135/2.8 in the studio which gives amazing results.

Tim

There is also the new DA* 55/1.4: http://www.bdimitrov.de/kmp/lenses/primes/normal/DA55f1.4.html

Sorry I can't help with the decision as I don't know very much about the 55 or the Sigma.

I don't see how there would be any difference in low-light auto focusing ability with any lens of about the same max aperture though. AF is controlled by the camera, not the lens.