Where can I find an Exakta-mount lens worth adapting in 2026?

Vintage-camera secondary markets (eBay, KEH, Foto-Walser, Japan-based MapCamera). Notable optics: Carl Zeiss Jena Biotar 58 mm f/2 (the original swirly-bokeh portrait lens), Tessar 50 mm f/2.8, Schneider Kreuznach Xenon 50 mm f/1.9, Meyer-Optik Trioplan 100 mm f/2.8 (bubble bokeh), Primotar 80 mm f/3.5. Prices range from $30 for common Tessars to $1500+ for clean original Trioplan 100 mm f/2.8 samples.

Can Exakta lenses adapt to Sony E or Canon RF?

Yes — pure mechanical Exakta-to-E and Exakta-to-RF adapters are widely available (Fotodiox, K&F Concept, Urth, NovoFlex) for $20-40. The 44.7 mm flange leaves abundant room for the adapter. Focus is manual, aperture is set on the lens. Exakta lenses use external auto-aperture levers, so most quality adapters include a small lever-pusher arm so the aperture pre-set ring still works; infinity focus is preserved.

What was special about the original Exakta camera?

The 1936 Kine Exakta is widely cited as the world's first practical 35 mm single-lens reflex camera, predating the Contax S (1949) and Asahiflex (1952). It introduced features adopted across SLRs for the next 60 years: rectangular eyepiece viewfinder, mechanical instant-return mirror (1948 retrofit), waist-level finder, interchangeable bayonet lens mount, and a left-hand-mounted shutter release (Exakta is the only major 35 mm SLR system with a left-side release).

Ihagee Dresden · Legacy SLR mount

Exakta — flange distance, protocol, and adapter compatibility

The world's first practical 35 mm SLR mount, introduced by Ihagee Dresden in 1936 on the Kine Exakta. Bayonet interface with a left-handed front-mounted shutter release. Pure mechanical — auto-aperture via external lever, no electrical contacts ever. Carl Zeiss Jena (Biotar, Tessar), Schneider Kreuznach (Xenon), and Meyer-Optik (Trioplan, Primotar) built the most-collected glass for it. Discontinued in 1972 with Ihagee's collapse, but Exakta lenses adapt cleanly onto every mirrorless mount thanks to the modest 44.7 mm flange.

Mount specifications

Flange focal distance: 44.7 mm
Throat diameter: 38 mm
Electronic protocol: Mechanical only (no electronic coupling)
Supported formats: full-frame, APS-C
Manufacturer: Ihagee Dresden
Introduced: 1936 (discontinued)
Status: Discontinued

Exakta on the flange-distance axis

Exakta sits at 44.7 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 Exakta lenses onto other bodies

You own Exakta 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 MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Canon RF body.
Body mount Canon FD flange 42 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Canon FD body.
Body mount Canon EF-M flange 18 mm	Mechanical MFno ISAp. ring1.5× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Canon EF-M body.
Body mount Nikon Z flange 16 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Nikon Z body.
Body mount Sony E (incl. FE) flange 18 mm	Mechanical MFno ISAp. ring	Fotodiox Exakta-NEX K&F Concept Exakta-NEX Generic Exa-NEX rings	Auto-aperture Exakta lenses use a side-mounted plunger to stop down — adapter doesn't actuate this; use the lens's manual A/M switch (where present) or stop down by hand. 26.7 mm flange clearance — comfortable adapter thickness.
Body mount Fujifilm X flange 17.7 mm	Mechanical MFno ISAp. ring1.5× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Fujifilm X body.
Body mount Fujifilm GFX (G-mount) flange 26.7 mm	Mechanical MFno ISAp. ringvignettes	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Fujifilm GFX (G-mount) body.
Body mount Micro Four Thirds flange 19.25 mm	Mechanical MFno ISAp. ring2× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Micro Four Thirds body.
Body mount L-Mount flange 20 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and L-Mount body.
Body mount Leica M flange 27.8 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Leica M body.
Body mount Canon RF (cine) flange 20 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Canon RF (cine) body.
Body mount C-mount flange 17.526 mm	Mechanical MFno ISAp. ring2.7× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and C-mount body.
Body mount Konica AR flange 40.5 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Exakta lens and Konica AR body.
Body mount Canon EF flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 0.7 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 Exakta 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 0.7 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 Exakta 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 -1.8 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 Exakta 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 0.2 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 Exakta 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 -0.8 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 Exakta 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 Pentax K flange 45.46 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 Exakta lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a Pentax K (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 -7.3 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 Exakta 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 0.7 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 Exakta 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 T-mount (T2) flange 55 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -10.3 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 Exakta 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 0.3 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 Exakta 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 1.2 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 Exakta 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 -1.3 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 Exakta 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 -0.8 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 Exakta 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 Exakta body

You own a Exakta 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 Exakta 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 Exakta body.
Lens mount Canon EF flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -0.7 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 -0.7 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 -2.7 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 1.8 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 Sony A / Minolta A flange 44.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -0.2 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 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 Pentax K flange 45.46 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 Canon EF (cine) flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -0.7 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 -0.3 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 -4.2 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 -1.2 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 1.3 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 0.8 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.

References

Common questions

Where can I find an Exakta-mount lens worth adapting in 2026?: Vintage-camera secondary markets (eBay, KEH, Foto-Walser, Japan-based MapCamera). Notable optics: Carl Zeiss Jena Biotar 58 mm f/2 (the original swirly-bokeh portrait lens), Tessar 50 mm f/2.8, Schneider Kreuznach Xenon 50 mm f/1.9, Meyer-Optik Trioplan 100 mm f/2.8 (bubble bokeh), Primotar 80 mm f/3.5. Prices range from $30 for common Tessars to $1500+ for clean original Trioplan 100 mm f/2.8 samples.
Can Exakta lenses adapt to Sony E or Canon RF?: Yes — pure mechanical Exakta-to-E and Exakta-to-RF adapters are widely available (Fotodiox, K&F Concept, Urth, NovoFlex) for $20-40. The 44.7 mm flange leaves abundant room for the adapter. Focus is manual, aperture is set on the lens. Exakta lenses use external auto-aperture levers, so most quality adapters include a small lever-pusher arm so the aperture pre-set ring still works; infinity focus is preserved.
What was special about the original Exakta camera?: The 1936 Kine Exakta is widely cited as the world's first practical 35 mm single-lens reflex camera, predating the Contax S (1949) and Asahiflex (1952). It introduced features adopted across SLRs for the next 60 years: rectangular eyepiece viewfinder, mechanical instant-return mirror (1948 retrofit), waist-level finder, interchangeable bayonet lens mount, and a left-hand-mounted shutter release (Exakta is the only major 35 mm SLR system with a left-side release).