Pentax HD DA 21mm f3.2 AL Limited lens review: Enhanced image qualityBy Kevin Carter - Monday January 13 2014 Lens Review
Pentax HD DA 21mm F3.2 AL Limited lens performance
Mounted on the new Pentax K-3 with its 24-Mpix sensor without the AA blur filter the new HD 21mm f3.2 AL Limited achieved a DxOMark lens score of 18 points. That’s a good but not great score for a moderately wide prime, and in part that’s due to the slightly lower than expected 11-P-Mpix peak sharpness score. Given the potential of the optical system sharpness is a little disappointing but it’s not the whole story.
Distortion is low and vignetting, if not low exactly for this type of lens, is at least well controlled.
Peripheral illumination is 1.1 Ev lower in the extreme corners than the center at maximum aperture but the transition isn’t abrupt, and besides it’s easy to remove if it’s troubling. A trace of vignetting can still be seen at f4 in the corners but it’s clear by f5.6.
Chromatic aberration is more troublesome, and it’s noticeable at times in the outer 50% of the frame. Stopping down helps reduce it but it remains in the extreme corners in our tests, though it is unlikely to be an issue in normal use.