Originally posted by Ascencio Who has better autofocus primes 85mm 1.4, 35mm 1.4, 20mm, 24mm, 135mm
The problem with some sigma lenses is they don't AF properly on pentax cameras, and calibration with the sigma dock can do little to fix it - for reasons that still remain unclear the Sigma ART lenses have AF issues at certain distances that make them practically unusable for some.
Originally posted by Rondec it is just that the bar is not typically set anywhere near perfection for f1.4 full frame lenses.
It never was a priority in the days of film, most lenses were fast because it made the focus screen brighter - not to satisfy bokeh jockeys who desire infinitesimally thin DOF . It has only been the past decade or so where extreme levels of optical performance have been in demand even at apertures as wide as f/0.95.
Originally posted by pres589 If the DA*55 didn't cover the full image circle presented by film or the K-1's sensor, vignetting wouldn't be removed simply by stopping down the lens, right? It'd be a hard edge of black that was always present, right?
Due to the effects of diffraction, the image circle of lenses actually gets bigger as you stop the lens down. Experienced LF photographers will tell you that.