Pentax's early M42 portrait lens — the Preset 105mm f/2.8 Takumar for close-up and portrait work.
The Asahi Pentax 105mm f/2.8 Preset in M42 is a fast medium telephoto from Asahi (Pentax) in the preset aperture configuration, predating the auto-aperture Takumar system. The 105mm f/2.8 specification provides portrait-length reach with a fast maximum aperture.
The lens delivers 105mm at f/2.8 maximum aperture with a preset aperture mechanism requiring manual pre-setting and stop-down before exposure, M42 screw mount, and full-frame 35mm coverage. Asahi optical quality is generally high across the M42 Pentax product range.
The 105mm f/2.8 preset occupies the portrait-telephoto range and is sought by adapters to modern mirrorless cameras for its fast aperture and Asahi rendering quality. The preset mechanism requires practice but functions reliably once mastered. M42 adapters are universally available.
Test preset aperture ring operation — both setting and stop-down rings should engage and release cleanly. Inspect elements for clarity and thoriated glass yellowing (Asahi used thorium oxide in some element formulas of this era). Check focus ring smoothness. Verify M42 thread coupling.