|Introduction | Pentax HD DA 15mm F4 ED AL Limited: Good center sharpness | Pentax HD DA 15mm F4 ED AL Limited Versus Competition | Conclusion|
Compared against the now discontinued smc version, and the $949 high-speed 14mm from the firm, the results are very similar, but the new version shows some slight improvements in labs, even if they might not bee noticed n in real world use. All three have slightly low sharpness at f4 but at f5.6 onwards the trio perform very similarly – each exhibits good center sharpness but with slightly lower edge performance. As you might expect the 14mm is faster - it has +2/3 stop advantage in transmission (at maximum aperture only) not a whole stop, but the new HD Limited has lower distortion and slightly better control of vignetting at f4.
We were curious to compare new lens with similar focal lengths from two independents – Samyang (sometimes branded as Rokinon in the US) and Sigma. Both can be found with Pentax mounts and although the Sigma is being phased out it can still be located on retailers’ shelves at $599. Besides the modest $299 price, the full-frame Samyang is notable for its sharpness. At f2.8 it still only has moderate sharpness but at f4 it’s good although lower at periphery.
Peak performance is at f5.6 with f8 being very similar to f4 in sharpness levels and uniformity. However, the Samyang has very noticeable distortion that’s not easy to correct. The Sigma on the other hand has good central sharpness at f4 but with notably poorer corners – and has slightly worse edge sharpness than the Pentax at f5.6-8.