Cosinon's fast telephoto for Pentax K — the 135mm f/2.8 with good speed.
The Cosinon 135mm f/2.8 is a fast telephoto prime from Cosina under the Cosinon brand name, designed for Pentax K-mount cameras. Cosinon was the lens brand used by Cosina for their independently sold optics as distinct from OEM production.
The lens delivers 135mm at f/2.8 maximum aperture with Pentax K coupling, manual focus and aperture, and full-frame 35mm coverage. Cosinon optical quality reflects Cosina's manufacturing standards for the period.
The 135mm f/2.8 is a fast telephoto for portrait and documentary work. The Cosinon brand indicates Cosina's own production rather than a rebadged product. Pentax K adapters make these lenses adaptable to modern cameras.
Test Pentax K coupling. Check aperture blade operation at f/2.8. Inspect elements. Verify focus ring smoothness.