What's the difference between T-mount and T2?

T-mount is the original M42 × 0.75 threaded interface introduced by Tamron in 1957, with 55 mm flange-to-thread spacing. T2 is the standardised variant Tamron defined in 1962 — same thread and same flange spacing, but with three lens-to-T-X-adapter alignment pins to ensure consistent rotational positioning. In modern usage the terms are interchangeable; every modern "T-mount" lens is actually T2.

Why does my T-mount lens need a separate T-X adapter for my camera?

T-mount is a lens-side interface only — the lens screws into a T-X adapter ring, and the T-X adapter is what carries the body-side mount. Each target body needs its own T-X variant: T-Nikon F, T-Canon FD, T-Canon EF, T-Sony E, T-Sony A, T-Fujifilm X, T-Canon RF, T-Nikon Z, T-MFT, T-L-Mount. The T-X adapter accounts for the body's specific flange depth, so the lens's optical design always sits at the same 55 mm flange relative to the body's sensor.

Is T-mount still being produced for new lenses in 2026?

Yes — actively, but primarily for telescope eyepieces, machine-vision optics, and Samyang / Walimex manual primes targeting the astrophotography market (the original Samyang 135 mm f/2 was a T-mount design before native-mount versions launched). Tamron itself moved to native bayonet mounts decades ago; T-mount survives as the de-facto standard for astronomy and microscopy, where a one-lens-many-bodies design matters more than autofocus.

Various (Tamron-originated standard) · Legacy SLR mount

T-mount (T2) — flange distance, protocol, and adapter compatibility

M42 × 0.75 thread originated by Tamron in 1957 (and later standardised as T-2 in 1962). Not a camera-mount in the conventional sense — T-mount lenses (Tamron Adaptall predecessors, Vivitar Series 1 zooms, Soligor primes, modern telescope eyepieces, Samyang manual primes) screw into a T-X adapter ring sized for the target body (T-Nikon F, T-Canon FD, T-EF, T-Sony E, T-RF, etc.). The lens's own flange-to-thread surface is 55 mm; the T-X adapter accounts for the body's actual flange. Still actively produced for astronomy and machine-vision optics.

Mount specifications

Flange focal distance: 55 mm
Throat diameter: 42 mm
Electronic protocol: Mechanical only (no electronic coupling)
Supported formats: full-frame, APS-C
Manufacturer: Various (Tamron-originated standard)
Introduced: 1957
Status: Active production

T-mount (T2) on the flange-distance axis

T-mount (T2) sits at 55 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 T-mount (T2) lenses onto other bodies

You own T-mount (T2) 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 EF flange 44 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Canon EF body.
Body mount Canon EF-S flange 44 mm	Mechanical MFno ISAp. ring1.5× crop	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Canon EF-S body.
Body mount Canon RF flange 20 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) 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 T-mount (T2) 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 T-mount (T2) lens and Canon EF-M body.
Body mount Nikon F flange 46.5 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Nikon F 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 T-mount (T2) lens and Nikon Z body.
Body mount Sony A / Minolta A flange 44.5 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Sony A / Minolta A body.
Body mount Sony E (incl. FE) flange 18 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Sony E (incl. FE) body.
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 T-mount (T2) 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 T-mount (T2) 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 T-mount (T2) 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 T-mount (T2) lens and L-Mount body.
Body mount M42 (Pentax / Praktica screw mount) flange 45.46 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and M42 (Pentax / Praktica screw 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 T-mount (T2) lens and Leica M body.
Body mount Pentax K flange 45.46 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.
Body mount PL (Positive Lock) flange 52 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and PL (Positive Lock) body.
Body mount Canon EF (cine) flange 44 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Canon EF (cine) 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 T-mount (T2) lens and Canon RF (cine) body.
Body mount Exakta flange 44.7 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.
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 T-mount (T2) lens and C-mount body.
Body mount Praktica B flange 44.4 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Praktica B 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 T-mount (T2) lens and Konica AR body.
Body mount Minolta SR / MC / MD flange 43.5 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Minolta SR / MC / MD body.
Body mount Olympus OM flange 46 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Olympus OM body.
Body mount Contax/Yashica (C/Y) flange 45.5 mm	Mechanical MFno ISAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Contax/Yashica (C/Y) body.

Adapting other lenses onto a T-mount (T2) body

You own a T-mount (T2) 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 Canon EF flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -11.0 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 Canon EF-S flange 44 mm	Speed booster MFIS lens-onlyAp. wheelvignettes	Speed Booster / focal-reducer family	Flange clearance is only -11.0 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 Nikon F flange 46.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -8.5 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 Sony A / Minolta A flange 44.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -10.5 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 M42 (Pentax / Praktica screw mount) flange 45.46 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.
Lens mount Pentax K flange 45.46 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.
Lens mount PL (Positive Lock) flange 52 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -3.0 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 Canon EF (cine) flange 44 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -11.0 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 Exakta flange 44.7 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.
Lens mount Praktica B flange 44.4 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -10.6 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 -11.5 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 Olympus OM flange 46 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -9.0 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 Contax/Yashica (C/Y) flange 45.5 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.

References

Common questions

What's the difference between T-mount and T2?: T-mount is the original M42 × 0.75 threaded interface introduced by Tamron in 1957, with 55 mm flange-to-thread spacing. T2 is the standardised variant Tamron defined in 1962 — same thread and same flange spacing, but with three lens-to-T-X-adapter alignment pins to ensure consistent rotational positioning. In modern usage the terms are interchangeable; every modern "T-mount" lens is actually T2.
Why does my T-mount lens need a separate T-X adapter for my camera?: T-mount is a lens-side interface only — the lens screws into a T-X adapter ring, and the T-X adapter is what carries the body-side mount. Each target body needs its own T-X variant: T-Nikon F, T-Canon FD, T-Canon EF, T-Sony E, T-Sony A, T-Fujifilm X, T-Canon RF, T-Nikon Z, T-MFT, T-L-Mount. The T-X adapter accounts for the body's specific flange depth, so the lens's optical design always sits at the same 55 mm flange relative to the body's sensor.
Is T-mount still being produced for new lenses in 2026?: Yes — actively, but primarily for telescope eyepieces, machine-vision optics, and Samyang / Walimex manual primes targeting the astrophotography market (the original Samyang 135 mm f/2 was a T-mount design before native-mount versions launched). Tamron itself moved to native bayonet mounts decades ago; T-mount survives as the de-facto standard for astronomy and microscopy, where a one-lens-many-bodies design matters more than autofocus.