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Adapter compatibility · Pentax / Ricoh → Contax / Yashica

Pentax K to Contax adapter compatibility

Mounting a Pentax K lens on a Contax/Yashica (C/Y) body — the feasibility verdict, AF / IS / aperture-control / infinity-focus outcome, image-circle relationship, official and reputable third-party adapter SKUs, and the caveats worth knowing before you buy.

Verdict at a glance

Speed booster
MFIS lens-onlyAp. wheel

Mount specs

Lens side

Pentax K

Flange distance
45.46 mm
Protocol
Pentax K (KAF/KAF2/KAF3/KAF4)
Type
DSLR

Body side

Contax/Yashica (C/Y)

Flange distance
45.5 mm
Protocol
Mechanical only
Type
legacy-SLR

The Pentax Klens’s flange distance (45.46 mm) is 0.04 mm shorter than the Contax body’s (45.5 mm). A mechanical adapter can only add distance between the lens and the sensor, never remove it, so a plain spacer cannot hold a Pentax K lens close enough to reach infinity focus. The verdict above calls for a focal reducer (Speed Booster) — its corrective optics bridge the deficit and add roughly a stop of light.

Flange-distance schematic. Two rails share a sensor plane on the right. The Contax body register measures 45.5 millimetres; the Pentax K lens needs only 45.46 millimetres, which is 0.04 millimetres shorter. The orange region marks the deficit a mechanical spacer cannot remove; a focal reducer is required.Sensor planeContax body · 45.5 mmPentax K lens · 45.46 mm−0.04 mm short
The Contax body holds any lens 45.5 mm off the sensor, but the Pentax K lens reaches infinity at 45.46 mm — 0.04 mm closer than the body allows. A mechanical adapter only adds distance, so a focal reducer (Speed Booster) is required to recover infinity focus.

Adapter examples

  • Speed Booster / focal-reducer family

Caveats

  • Flange clearance is only -0.0 mm — a plain mechanical adapter cannot reach infinity focus; a focal reducer (Speed Booster) with optical glass is required.
  • Speed Boosters typically widen the effective focal length (~0.71×) and add ~1 stop of light, which can be desirable on crop bodies.

Common questions

Will Pentax K lenses autofocus on a Contax/Yashica (C/Y) body through an adapter?
No — Pentax K → Contax adapters are mechanical only. Focus is fully manual; rely on the Contax body's focus peaking and magnify-to-focus aids to nail focus.
Does in-lens image stabilization (IS / VR / OS) still work through a Pentax K → Contax adapter?
Lens-side only — the Pentax K lens's IS / VR / OS unit operates, but it cannot synchronise with the Contax body's IBIS, so the dual-axis stabilisation native Contax lenses enjoy isn't available. Lens-side stabilisation still delivers most of the practical benefit.
What's the most-recommended Pentax K → Contax adapter?
No SKU in our curated catalogue covers Pentax K → Contax yet. Adapter examples photographers commonly use include the Speed Booster / focal-reducer family. Pair compatibility is mostly mechanical, so any well-built adapter at the correct flange distance should work — pick on build quality and tripod-foot integration.

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