Best lenses for Pentax K-3: Recommended wide angle, telephoto and standard lensesBy Kevin Carter - Tuesday January 07 2014 Lens Recommendations
Sigma’s new full-frame 35mm f1.4 DG HSM is also available with a Pentax K mount and it comes as little surprise to see it perform well on the Pentax K-3. Even though it’s the best performing model in this category it doesn’t exhibit the quite the same performance as we've witnessed on the Nikon D7100.
On that camera the Sigma has excellent sharpness across the field at maximum aperture through to f4, with only very slight drop in the corners. And, stopped down to f5.6, sharpness extends right the way to the corners. However, that’s not the case with the Pentax combination. The centers are sharp but the periphery is someway behind. Even at f8 the corners are still very slightly behind, and at f11 diffraction lowers sharpness significantly. In fact, it performs very similarly to the Sony mount version on the SLT-A77 - a camera with an AA filter as well as a semi-silvered (SLT) mirror in the light path. Intriguingly all three cameras have related sensors. Nevertheless, the Sigma is a good performer and it’s competitively priced, given the high-speed f1.4 maximum aperture.
In joint second place in this category are the smc and HD versions of the DA 35mm f2.8 Macro Limited, which isn’t surprising given the reputation. With the same DxOMark score, making it technically joint second, is the modestly priced $220 smc DA 35mm f2.4 AL. It’s neither a macro (the DA Limited can go to 1:1) or as well made (it doesn’t even have any distance markings, and the build is a little low rent), but it’s a good performer optically. This lens has good uniformity even if it can’t match the sharpness of the DA 35mm f2.8 Macro Limited model till f4. The Sigma may be the sharpest overall, but if you’re unsure about the field of view (it’s one of the most difficult to master) then the Pentax 35mm f2.4 is a good first choice.