Overview

The SMC Pentax-M 50mm f/4 Macro is a classic Tessar-design lens (4 elements in 3 groups) from 1977–1984. It is sharp corner-to-corner from f/4, with a flat field, no distortion, reasonable contrast, and almost no chromatic aberration. Weaknesses include a five-blade aperture producing pentagonal bokeh that some find unappealing, and a maximum magnification of 1:2 (0.45x) requiring extension tubes for 1:1. Build is neat with reproduction ratios on the focus ring for easy reading, but lacks in-camera aperture control. It suits macro photographers who prioritize sharpness and flat field over bokeh and are comfortable with manual aperture.