Zeiss's Contax wide-angle prime — the Distagon T* 18mm f/4, rectilinear manual-focus glass for the C/Y mount.
The Zeiss Distagon T* 18mm f/4 was a wide-angle prime for the Contax/Yashica mount, among the first optics released with the Contax SLR system in the mid-1970s. It offered a rectilinear ultra-wide view within the Distagon retrofocus line.
This is a manual-focus C/Y-mount lens with an 18mm focal length and a maximum aperture of f/4. The retrofocus Distagon layout kept horizontals and verticals straight across the frame. Additional optical specifications are omitted where they cannot be confirmed.
At 18mm the lens delivers a broad rectilinear field suited to landscape, architecture and interiors where distortion control matters. The T* multi-coating helped maintain contrast when shooting toward bright light with a wide front element.
On the second-hand market this is a collectible wide-angle that holds its value well. Look for internal haze, fungus and separation, check the front and rear elements for coating wear, and make sure the aperture ring clicks positively and the blades are dry. It works on mirrorless with a C/Y adapter.