Pentax's affordable 75mm-equivalent portrait prime for K-mount APS-C bodies.
The Pentax SMC DA 50mm f/1.8 was introduced in 2012 as an affordable fast prime for Pentax K-mount APS-C bodies. Giving a 75mm equivalent field of view, it serves as a classic portrait lens on cameras like the K-3, K-5, and K-70. It filled a gap in the Pentax lineup for a budget-friendly fast fifty.
Optically it performs well for the price. Centre sharpness is good from f/1.8 and excellent by f/2.8. Bokeh is reasonably smooth with seven aperture blades, though not as refined as the more expensive DA* 55mm f/1.4. Chromatic aberration is visible wide open but correctable in post. AF is driven by the in-body screw-drive motor.
Pentax K mount, DA designation meaning APS-C optimised. Filter thread is 52mm. Weight is approximately 122 grams — extremely light. The build is mostly plastic with a metal mount. No weather sealing, unlike many of Pentax's higher-end DA* lenses. No image stabilisation — rely on Pentax's excellent in-body Shake Reduction.
Very affordable on the used market, often under £80. Check for smooth focus ring operation and clean optics. The plastic build means careful handling is important. Outstanding value for Pentax shooters wanting shallow depth of field on a budget — the DA* 55mm f/1.4 is the upgrade path for those wanting premium quality.