Is the Pentax K mount still being made in 2026?

Yes — Pentax (under Ricoh ownership since 2011) continues to build K-mount DSLRs (Pentax K-3 Mark III, K-1 Mark II, KF) and ships new K-mount lenses (HD Pentax-D FA 50 mm f/1.4 SDM AW, HD Pentax-D FA 21 mm f/2.4ED Limited DC WR). Pentax is the only major manufacturer that has never released a consumer mirrorless body, citing optical-viewfinder commitment as the differentiator.

Do older manual-focus K-mount lenses work on a modern Pentax K-1 Mark II?

Yes — every K-mount lens since 1975 mounts and operates, including pre-A, K, KA, KAF, KAF2, KAF3, and KAF4 generations. Older manual lenses give stopped-down metering only; autofocus, aperture priority, and in-body shake reduction all work on AF and electronic-aperture lenses. Pentax's backward-compatibility track record across 50+ years is unmatched by any other manufacturer.

Can I adapt Pentax K lenses to Sony E or Canon RF?

Yes — pure mechanical K-to-E and K-to-RF adapters are widely available (Fotodiox, K&F Concept, Urth) for $15-30. Aperture must be set manually on the lens for K, KA, and earlier generations with an aperture ring. KAF4 lenses (electromagnetic-only aperture, no ring) cannot be controlled without an aperture-driving adapter, which doesn't currently exist commercially for K-mount on any mirrorless target.

Pentax / Ricoh · DSLR / SLR mount

Pentax K — flange distance, protocol, and adapter compatibility

Pentax's bayonet mount since 1975, with full backward compatibility — even a 1975 K-mount manual lens fits a modern Pentax K-1 II. Multiple electronic generations (KAF / KAF2 / KAF3 / KAF4) add screw-drive AF, in-lens motors, and electronic aperture progressively. Limited third-party adapter market because Pentax has no mirrorless line of its own.

Mount specifications

Flange focal distance: 45.46 mm
Throat diameter: 44 mm
Electronic protocol: Pentax K (KAF/KAF2/KAF3/KAF4)
Supported formats: full-frame, APS-C
Manufacturer: Pentax / Ricoh
Introduced: 1975
Status: Active production

Pentax K on the flange-distance axis

Pentax K sits at 45.46 mm — highlighted in orange below. The flange-distance gap between the mirrorless and SLR clusters is the room a mechanical adapter occupies; that gap is why almost every SLR lens adapts onto every mirrorless body, and why the reverse is mechanically impossible.

Flange focal distance (mm)SLR / DSLRMirrorlessRangefinderMedium-format mirrorlessCinemaLegacy SLR

Adapting Pentax K lenses onto other bodies

You own Pentax K glass and want to mount it on a body with a different lens mount. Rows are sorted by feasibility.

Body mount	Result	Adapter examples	Caveats
Body mount Canon RF flange 20 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Canon RF body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Canon FD flange 42 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Canon FD body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Canon EF-M flange 18 mm	Mechanical MFIS lens-onlyAp. wheel1.5× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Canon EF-M body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Nikon Z flange 16 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Nikon Z body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Sony E (incl. FE) flange 18 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Sony E (incl. FE) body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Fujifilm X flange 17.7 mm	Mechanical MFIS lens-onlyAp. wheel1.5× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Fujifilm X body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Fujifilm GFX (G-mount) flange 26.7 mm	Mechanical MFIS lens-onlyAp. wheelvignettes	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Fujifilm GFX (G-mount) body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Micro Four Thirds flange 19.25 mm	Mechanical MFIS lens-onlyAp. wheel2× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Micro Four Thirds body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount L-Mount flange 20 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and L-Mount body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Leica M flange 27.8 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Leica M body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Canon RF (cine) flange 20 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Canon RF (cine) body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount C-mount flange 17.526 mm	Mechanical MFIS lens-onlyAp. wheel2.7× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and C-mount body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Konica AR flange 40.5 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Pentax K lens and Konica AR body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Body mount Canon EF flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 1.5 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Canon EF (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Canon EF-S flange 44 mm	Speed booster MFIS lens-onlyAp. wheel1.5× crop	Speed Booster / focal-reducer family	Flange clearance is only 1.5 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Canon EF-S (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Nikon F flange 46.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -1.0 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Nikon F (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Sony A / Minolta A flange 44.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 1.0 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Sony A / Minolta A (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount M42 (Pentax / Praktica screw mount) flange 45.46 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a M42 (Pentax / Praktica screw mount) (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount PL (Positive Lock) flange 52 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -6.5 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a PL (Positive Lock) (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Canon EF (cine) flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 1.5 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Canon EF (cine) (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Exakta flange 44.7 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 0.8 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Exakta (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount T-mount (T2) flange 55 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -9.5 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a T-mount (T2) (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Praktica B flange 44.4 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 1.1 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Praktica B (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Minolta SR / MC / MD flange 43.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 2.0 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Minolta SR / MC / MD (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Olympus OM flange 46 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -0.5 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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Olympus OM (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.
Body mount Contax/Yashica (C/Y) flange 45.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	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.	Speed Booster equivalence calculator Plug in any Pentax K lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Contax/Yashica (C/Y) (APS-C), plus the full-frame equivalent angle of view after the body's crop stacks on top. Lens focal length (mm)Max aperture (f/N)Focal-reducer family Effective focal length 35.5 mm 50.0 mm × 0.71 on the reducer. Effective aperture f/1.28 0.99 stops brighter than f/1.80. Full-frame equiv. angle of view 53.3 mm 35.5 mm × 1.5× (APS-C sensor crop). A focal reducer concentrates the lens's image circle, so both focal length and f-number scale by the same ratio (stops gained = `−2 · log₂(ratio)`). The body's crop factor still applies on top — the full-frame-equivalent angle-of-view multiplier is ratio × body crop. Calculator is informational; verify against the adapter vendor's per-lens compatibility chart before purchase.

Adapting other lenses onto a Pentax K body

You own a Pentax K body and want to mount glass from other systems. Mirrorless-lens-onto-DSLR-body combinations are omitted (rear element collides with the mirror box).

Lens mount	Result	Adapter examples	Caveats
Lens mount PL (Positive Lock) flange 52 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between PL (Positive Lock) lens and Pentax K body.
Lens mount T-mount (T2) flange 55 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Pentax K body.
Lens mount Canon EF flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -1.5 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.
Lens mount Canon EF-S flange 44 mm	Speed booster MFIS lens-onlyAp. wheelvignettes	Speed Booster / focal-reducer family	Flange clearance is only -1.5 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.
Lens mount Canon FD flange 42 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -3.5 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.
Lens mount Nikon F flange 46.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 1.0 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.
Lens mount Sony A / Minolta A flange 44.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -1.0 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.
Lens mount M42 (Pentax / Praktica screw mount) flange 45.46 mm	Speed booster MFno ISAp. ring	Pentax K-mount M42 adapter (official thin spacer)	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.
Lens mount Canon EF (cine) flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -1.5 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.
Lens mount Exakta flange 44.7 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -0.8 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.
Lens mount Praktica B flange 44.4 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -1.1 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.
Lens mount Konica AR flange 40.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -5.0 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.
Lens mount Minolta SR / MC / MD flange 43.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -2.0 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.
Lens mount Olympus OM flange 46 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 0.5 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.
Lens mount Contax/Yashica (C/Y) flange 45.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	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.

Adapter SKU teardown

Curated adapter SKUs that involve the Pentax K mount on either side, with the operational specifics — body-side electronic contact count, firmware-update path, weather sealing, and whether optical glass is in the path.

K&F Concept Pentax K-NEX Pro
released 2019
Pentax K lens → Sony E (incl. FE) body
- no firmware updates
- not weather sealed
- no glass — pass-through
- Pro-line Pentax K (K / KA / KAF — covering SMC Takumar bayonet, A-series with aperture, F / FA / DA AF lenses) onto Sony E. Mechanical-only; AF and electronic aperture are not passed through.
- Copper-inset bayonet for tight rotational fit. SMC FA Limited (31 mm f/1.8, 43 mm f/1.9, 77 mm f/1.8) and DA Limited (15 / 21 / 35 / 40 / 70 mm) primes mount cleanly with infinity-focus calibrated.
K&F Concept PK-NEX
released 2016
Pentax K lens → Sony E (incl. FE) body
- no firmware updates
- not weather sealed
- no glass — pass-through
- Pentax K bayonet (SMC Pentax K / M / A glass and SMC Takumar-K) onto Sony E. Mechanical-only ring — no AF, no electronic aperture. K and M lenses set aperture directly on the ring; A-series lenses must be turned off the green 'A' position so the ring controls the diaphragm.
- The 45.46 mm K flange clears Sony E's 18 mm by 27.46 mm — a flat glassless ring with infinity preserved. Fits the cult FA Limited primes (31/1.8, 43/1.9, 77/1.8) as readily as the cheap SMC-M classics.

References

https://en.wikipedia.org/wiki/Pentax_K-mount

Common questions

Is the Pentax K mount still being made in 2026?: Yes — Pentax (under Ricoh ownership since 2011) continues to build K-mount DSLRs (Pentax K-3 Mark III, K-1 Mark II, KF) and ships new K-mount lenses (HD Pentax-D FA 50 mm f/1.4 SDM AW, HD Pentax-D FA 21 mm f/2.4ED Limited DC WR). Pentax is the only major manufacturer that has never released a consumer mirrorless body, citing optical-viewfinder commitment as the differentiator.
Do older manual-focus K-mount lenses work on a modern Pentax K-1 Mark II?: Yes — every K-mount lens since 1975 mounts and operates, including pre-A, K, KA, KAF, KAF2, KAF3, and KAF4 generations. Older manual lenses give stopped-down metering only; autofocus, aperture priority, and in-body shake reduction all work on AF and electronic-aperture lenses. Pentax's backward-compatibility track record across 50+ years is unmatched by any other manufacturer.
Can I adapt Pentax K lenses to Sony E or Canon RF?: Yes — pure mechanical K-to-E and K-to-RF adapters are widely available (Fotodiox, K&F Concept, Urth) for $15-30. Aperture must be set manually on the lens for K, KA, and earlier generations with an aperture ring. KAF4 lenses (electromagnetic-only aperture, no ring) cannot be controlled without an aperture-driving adapter, which doesn't currently exist commercially for K-mount on any mirrorless target.