A vintage 50mm f/1.7 standard prime lens for Contax/Yashica mount.
The Carl Zeiss Planar T* 50mm f/1.7 AEJ is the slower-aperture companion to the f/1.4 in the Contax/Yashica lens range, Japan-manufactured (AEJ) by Kyocera under Carl Zeiss licence. The f/1.7 version uses a different optical formula specifically designed for the f/1.7 aperture, and is regarded as exceptionally sharp wide-open compared to the f/1.4 at its respective maximum aperture.
50mm focal length, f/1.7 maximum aperture, Carl Zeiss T* multi-coating, Contax/Yashica (C/Y) bayonet mount, Japan-manufactured (AEJ designation).
The Planar T* 50mm f/1.7 is widely regarded as one of the sharpest standard lenses at its maximum aperture among all Contax/Yashica offerings. The f/1.7 formula's optical demands are less extreme than f/1.4, enabling tighter correction at wide-open. A popular adapted lens for mirrorless cameras alongside the f/1.4.
Inspect for fungus, haze, and T* coating condition. Check aperture blades for oil. Confirm C/Y bayonet engagement. Test focus helicoid smoothness. Compare with the f/1.4 version: the f/1.7 is generally preferred for wide-open sharpness; the f/1.4 for maximum light gathering.