The DA*55 easily wins here, though the Sigma has its virtues. What these casual samples (and almost any professional lens test you'll ever see, for some stupid reason) don't show you is how they perform stopped down by only 1/3 and 2/3 stops.
Very few lenses are great wide open (and most that are cost $1000+ or $1000+++), but the sign of a top performing lens is how it does
before it's stopped down by a full stop. If it takes a full stop to get good IQ the lens is marginal, at best. That's what's so impressive about the DA*55 - like the FA*85, it has very high IQ at f/1.6 or f/1.8. That's excellent performance, especially for such a fast lens.
BTW, the FA50/1.4 (or any of its F/FA brethren - I've owned 3 of the 4) can't hold a candle to the DA*55 until stopped down to at least f/2.8 (which defeats the whole purpose of having a fast 50, after all). The DA*55 (or the FA43, for that matter) is a much better choice. (However, in terms of usable images, the DA*55 is still at least a
full stop faster than the FA43 in practice).
The DA*55 can have absolutely beautiful OOF backgrounds. But you also need to be aware that in a few situations it can create some of the harsher backgrounds I've seen from a lens (for example, some backgrounds with bushes or similar elements come out poorly - to the point of distraction, I think). However, IMO it's worth the risk for the high quality it usually produces. If you haven't already looked, please see the PPG for examples of both the impressive sharpness and image isolation at f/1.6 or f/1.8, as well as the harsh or busy backgrounds in (fortunately) only a few of the images.
PENTAX : Select a PENTAX interchangeable lens camera or a lens model
Despite its one potential shortcoming, the DA*55 is one of the most impressive, fast lenses available on any DSLR, especially amongst AF models.
The Sigma may have less defined OOF areas, with a more blurry effect. Some people prefer this. The problem is the
IN Focus areas exhibit similar characteristics. Thus your subject stands out more nicely with the DA*55, despite the risk of occasional harsh backgrounds.
Last edited by DSims; 01-15-2014 at 03:33 AM.