Contax to Sony E adapter compatibility

Contax/Yashica onto Sony α is the canonical home for adapted C/Y glass, and the maths is the reason. The C/Y bayonet sits 45.5 mm from the film plane; Sony E is 18.0 mm. That 27.5 mm of clearance is more than enough for a plain glassless ring, so infinity focus is fully preserved with no corrective optics — the opposite of the C/Y → Canon EF case, where only ~1.5 mm of clearance forces a focal-reducer. On a full-frame α body (α7 IV, α7R V, α7C II, α1, α9 III) you also keep each lens's designed field of view.

Because C/Y was a purely mechanical mount — manual focus, an aperture ring on every lens, and no electrical contacts in any iteration — every adapter on the market is a dumb CNC ring. There is nothing to autofocus and nothing to meter electronically; you focus by hand and set the aperture on the lens. Four builds cover the price spectrum:

Fotodiox, K&F Concept, and Urth all ship glassless C/Y-to-E rings in the $15–50 band — perfectly serviceable for occasional use, with K&F and Urth the better-machined of the budget three. Novoflex's C/Y-NEX is the premium German option (~$200): tighter tolerances, no rotational play, and a properly flat lens-side register, which matters if you shoot the fast Planars wide open where a fraction of a degree of tilt shows up as a soft corner.

The glass is the whole point of this pairing. The Carl Zeiss Planar T* 50 mm f/1.4 and — above all — the Planar T* 85 mm f/1.4 are the headline reason photographers chase C/Y bodies on the used market: the 85 is one of the most revered portrait lenses ever built, with a rendering signature (high micro-contrast, gentle out-of-focus falloff, the warm T* colour) that modern Sony-Zeiss FE glass deliberately echoes but doesn't replicate. The Distagon 28 mm f/2.8, Sonnar 135 mm f/2.8, and the pocketable Tessar 45 mm f/2.8 pancake round out the most-adapted set, and the catalogue carries the rest of the C/Y Zeiss line beyond it: the Distagon 35 f/2.8 and Distagon 25 f/2.8 for the wide end, the Makro-Planar 60 f/2.8 for 1:2 close-up work, the Planar 100 f/2 medium-tele portrait, and the Vario-Sonnar 28-85 as a one-lens walk-around zoom.

Two buying notes specific to C/Y. First, lenses carry a factory origin code: AEG/MMG marks the German (Oberkochen) production prized for build quality, while AEJ/MMJ marks the Japanese copies made under Zeiss licence by Kyocera — optically near-identical and meaningfully cheaper. Second, the budget Yashica ML line (the ML 50 mm f/1.9, for one) shares the exact same mount, giving a sub-$50 way to try the system before committing to Zeiss prices. On the body side, Sony IBIS works at a user-entered focal length, focus peaking plus magnify make manual focus comfortable, and EXIF will not record the aperture you set on the ring — a minor metadata quirk, not a functional one.