{"lens":{"id":"m42","displayName":"M42 (Pentax / Praktica screw mount)","manufacturer":"Various","flangeDistanceMm":45.46,"electronicProtocol":"mechanical-only"},"body":{"id":"pentax-k","displayName":"Pentax K","manufacturer":"Pentax / Ricoh","flangeDistanceMm":45.46,"electronicProtocol":"Pentax K (KAF/KAF2/KAF3/KAF4)"},"compat":{"lensMountId":"m42","bodyMountId":"pentax-k","feasibility":"requires-glass","af":"n/a","is":"n/a","aperture":"manual-ring","infinityFocus":"requires-correction","adapterExamples":["Pentax K-mount M42 adapter (official thin spacer)"],"caveats":["M42 flange 45.46 mm equals Pentax K flange 45.46 mm — Pentax's adapter is essentially a thin alignment ring.","Infinity focus preserved exactly; no glass involved."],"formatNote":{"match":"match","lensFormat":"full-frame","bodyFormat":"full-frame","cropFactor":null,"message":"Lens image circle (full-frame) matches body sensor (full-frame) — no crop or vignetting concern."}}}