Cosina's telephoto for Pentax — the 100mm f/3.5 in PKA mount with auto aperture.
The Cosina 100mm f/3.5 in Pentax PKA mount is a medium telephoto prime from Cosina for the Pentax K-A system. PKA (Pentax K-A) indicates the lens has the additional aperture-coupling pin introduced in the KA series for program auto-exposure modes, as distinct from the basic K mount.
The lens delivers 100mm at f/3.5 maximum aperture with Pentax PKA coupling for program AE modes on compatible K-A series and later bodies, manual focus, and full-frame 35mm coverage.
The PKA coupling ensures full automatic exposure functionality on Pentax KA and newer bodies. The 100mm focal length provides portrait-length perspective with adequate working distance. Cosina's optical quality is generally above budget-brand alternatives.
Verify PKA coupling operation with a compatible Pentax body. Test aperture ring and focus ring. Inspect elements for clarity.