SMC Pentax-M 50 mm f/2 Lens

The SMC Pentax-M 50 mm f/2 is a compact, manual-focus standard prime lens for Pentax K-mount 35 mm and full-frame digital SLRs, produced from 1979 to 1985. It features a simple 5-element/5-group optical design, a 6-blade automatic diaphragm, and Pentax’s Super Multi-Coating (SMC) for improved contrast and flare resistance. With a maximum aperture of f/2, it offers decent low-light performance and shallow depth-of-field, while delivering solid sharpness and pleasing bokeh—especially when stopped down.

The lens focuses down to 0.45 m, uses a 49 mm filter thread, and weighs just 160 g in a compact 63 × 31 mm all-metal barrel (early versions). Later production runs used plastic components from the A-series to reduce cost, resulting in a lighter 138 g version with a slightly different aperture mechanism. Though often dismissed as a budget “kit lens,” it remains a surprisingly capable and affordable entry point into vintage Pentax glass.