Canon · DSLR / SLR mount

Canon EF — flange distance, protocol, and adapter compatibility

Canon's all-electronic SLR mount, introduced with the EOS system in 1987. Fully fly-by-wire — every EF lens has an in-lens AF motor and an electronic aperture; the body never mechanically couples to the lens. Compatible with EF, EF-S (APS-C bodies only), and EF-M (mirrorless via separate flange). The dominant base for cross-brand adaptation onto mirrorless thanks to thin profile and pure-electronic interface.

Mount specifications

Flange focal distance: 44 mm
Throat diameter: 54 mm
Electronic protocol: Canon EF
Supported formats: full-frame, APS-H, APS-C
Manufacturer: Canon
Introduced: 1987
Status: Active production

Adapting Canon EF lenses onto other bodies

You own Canon EF 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
Canon EF (cine) flange 44 mm	Native AF fullIS fullAp. electronic	no adapter required — stills EF glass mounts natively on Canon EF-mount cinema bodies (C200, C300 Mk II, C500 Mk II in EF mode)	Cinema EF bodies expose every stills-EF feature: full AF (where the lens supports it), in-lens IS, and electronic aperture. Servo zoom control (4-pin Servo connector on Canon's cine zooms) is not supported by stills EF lenses — irrelevant for primes.
Canon RF flange 20 mm	Mechanical AF fullIS fullAp. electronic	Canon EF-EOS R (plain) Canon EF-EOS R with Control Ring Canon EF-EOS R Drop-In Filter (Variable ND / Circular Polarizer)	Every Canon EF lens since 1987 preserves full AF, IS, and electronic aperture. EF-S lenses auto-crop to APS-C; full-frame RF bodies switch to 1.6× crop mode.
Canon EF-M flange 18 mm	Mechanical AF fullIS fullAp. electronic1.5× crop	Canon EF-EOS M	1.6× crop applies on every M-system body.
Nikon Z flange 16 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Canon EF lens and Nikon Z body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Sony E (incl. FE) flange 18 mm	Mechanical AF fullIS fullAp. electronic	Sigma MC-11 EF-E Metabones EF-E Mark V Viltrox EF-E5 / EF-NEX IV Fringer EF-NZ (when paired with similar smart-EF adapters)	AF speed and tracking depends on lens; Sigma's own EF lenses with MC-11 perform closest to native. Some third-party EF lenses (Tamron, older Sigma) have known AF quirks — check per-lens compatibility lists.
Fujifilm X flange 17.7 mm	Mechanical AF fullIS fullAp. electronic1.5× crop	Fringer EF-FX Pro II Fringer EF-FX2	Fringer covers most modern Canon EF lenses with phase-detect AF on X-Trans bodies. 1.5× crop applies (X-mount is APS-C).
Fujifilm GFX (G-mount) flange 26.7 mm	Mechanical AF partialIS lens-onlyAp. electronicvignettes	Fringer EF-GFX Pro Steelsring EF-GFX	Image circle of EF lenses may vignette on the 44×33 mm GFX sensor — many users crop to 35 mm capture mode. AF preserved on a curated list of EF lenses; check the adapter maker's compatibility chart.
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 Canon EF lens and Micro Four Thirds body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
L-Mount flange 20 mm	Mechanical AF fullIS fullAp. electronic	Sigma MC-21 EF-L	MC-21 has the best AF coverage with Sigma's own EF lenses; Canon-brand EF lens support varies by model. Tamron and some older third-party EF lenses are not officially supported.
Leica M flange 27.8 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Canon EF lens and Leica M body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Canon RF (cine) flange 20 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Canon EF lens and Canon RF (cine) body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
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 Canon EF lens and C-mount body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Konica AR flange 40.5 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Canon EF lens and Konica AR body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
Canon EF-S flange 44 mm	Speed booster MFIS lens-onlyAp. wheel1.5× crop	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.
Nikon F flange 46.5 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -2.5 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.
Sony A / Minolta A flange 44.5 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.
M42 (Pentax / Praktica screw mount) flange 45.46 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.
Pentax K flange 45.46 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.
PL (Positive Lock) flange 52 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -8.0 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.
Exakta flange 44.7 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.
T-mount (T2) flange 55 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.
Praktica B flange 44.4 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only -0.4 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.
Minolta SR / MC / MD flange 43.5 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.

Adapting other lenses onto a Canon EF body

You own a Canon EF 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
Canon EF (cine) flange 44 mm	Native MF—Ap. electronic	no adapter required — EF-cine glass mounts natively on EF bodies	EF-cine lenses are mechanically and electronically the EF mount with a reinforced collar and cine-geared rings — they mount native on every EF body. Canon CN-E primes carry electronic aperture but no AF motor; iris is body-controlled, focus is fully manual by design.
Nikon F flange 46.5 mm	Mechanical MFIS lens-onlyAp. wheel	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between Nikon F lens and Canon EF body. Lens has no aperture ring; choose an adapter with a built-in aperture-control wheel.
PL (Positive Lock) flange 52 mm	Mechanical MFIS lens-onlyAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between PL (Positive Lock) lens and Canon EF body.
T-mount (T2) flange 55 mm	Mechanical MFIS lens-onlyAp. ring	generic mechanical adapter ring (multiple vendors)	Mechanical adapter only — no electronic communication between T-mount (T2) lens and Canon EF body.
Canon EF-S flange 44 mm	Speed booster MFIS lens-onlyAp. wheelvignettes	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.
Sony A / Minolta A flange 44.5 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.
M42 (Pentax / Praktica screw mount) flange 45.46 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.
Pentax K flange 45.46 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.
Exakta flange 44.7 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.
Praktica B flange 44.4 mm	Speed booster MFIS lens-onlyAp. wheel	Speed Booster / focal-reducer family	Flange clearance is only 0.4 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.
Konica AR flange 40.5 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.
Minolta SR / MC / MD flange 43.5 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.

Adapter SKU teardown

Curated adapter SKUs that involve the Canon EF 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.

Canon EF-EOS R
released 2018
Canon EF lens → Canon RF body
- 12 body-side contacts
- no firmware updates
- weather sealed
- no glass — pass-through
- Canon-first-party adapter for EF / EF-S → RF / RF-S bodies. Preserves AF, IS, electronic aperture on every EF lens since 1987.
- Three variants: plain, Control Ring (extra rotation ring), Drop-In Filter (variable ND or circular polarizer slides in).
Sigma MC-11
released 2016
Canon EF lens → Sony E (incl. FE) body
- 9 body-side contacts
- firmware updatable
- not weather sealed
- no glass — pass-through
- Excellent native-like AF performance with Sigma's own EF Art and Sports lenses; Canon-brand EF lens support varies by model.
- Firmware-updatable via USB; FW v1.40 (2018) added several Tamron and Canon lens compatibility entries.
Sigma MC-21
released 2019
Canon EF lens → L-Mount body
- 12 body-side contacts
- firmware updatable
- not weather sealed
- no glass — pass-through
- Sigma's bridge from Canon EF + Sigma SA into the L-Mount Alliance ecosystem (Leica SL / CL, Panasonic Lumix S, Sigma fp).
- Best with Sigma's own EF Art / Contemporary / Sports lenses; Canon-brand EF compat is curated and listed on Sigma's published chart.
Metabones EF-E Mark V
released 2017
Canon EF lens → Sony E (incl. FE) body
- 11 body-side contacts
- firmware updatable
- not weather sealed
- no glass — pass-through
- Long-running EF-on-Sony adapter; Mark V adds improved phase-detect AF support on PDAF-capable Sony bodies.
- Firmware-updatable via the USB port on the side of the adapter.
Metabones Speed Booster ULTRA 0.71× EF-E
released 2014
Canon EF lens → Sony E (incl. FE) body
- 11 body-side contacts
- firmware updatable
- not weather sealed
- optical glass in path (focal reducer)
- Focal reducer for APS-C Sony E bodies (a6xxx series) — multiplies aperture by ~1 stop and reduces focal length by 0.71×, effectively letting EF full-frame lenses cover the APS-C sensor with extra light.
- Not for full-frame E-mount bodies (image circle won't cover the sensor).
Viltrox EF-EOS R5 (autofocus EF-to-RF)
released 2024
Canon EF lens → Canon RF body
- 12 body-side contacts
- firmware updatable
- not weather sealed
- no glass — pass-through
- Third-party alternative to Canon's official EF-EOS R; significantly cheaper, similar AF behaviour on most EF lenses.
- Firmware-updatable via USB-C, which is uncommon for the price point.
Viltrox EF-NEX IV (EF-E)
released 2018
Canon EF lens → Sony E (incl. FE) body
- 9 body-side contacts
- firmware updatable
- not weather sealed
- no glass — pass-through
- Budget EF-on-Sony adapter with electronic communication and firmware-updatable AF support.
- AF performance lags Metabones / MC-11 with non-Sigma EF lenses but is workable for static subjects.
Fringer EF-FX Pro II
released 2020
Canon EF lens → Fujifilm X body
- 9 body-side contacts
- firmware updatable
- not weather sealed
- no glass — pass-through
- Most reliable EF-on-Fuji-X adapter for phase-detect AF; manufacturer publishes a maintained per-lens compatibility list.
- Firmware updates over USB have continued for years post-release.
Fringer EF-GFX Pro
released 2019
Canon EF lens → Fujifilm GFX (G-mount) body
- 9 body-side contacts
- firmware updatable
- not weather sealed
- no glass — pass-through
- Brings EF lenses onto Fuji GFX medium-format bodies with AF on a curated list. Image circle of EF lenses may vignette on the 44×33 mm sensor — users often crop to 35 mm capture mode.
- Firmware-updatable via USB to track new EF lens releases.
Canon EF-EOS M
released 2012
Canon EF lens → Canon EF-M body
- 11 body-side contacts
- no firmware updates
- not weather sealed
- no glass — pass-through
- Canon's adapter from EF / EF-S onto the EOS M (EF-M) APS-C mirrorless line. Discontinued in spirit as Canon shifted M-line to RF-S in 2023.
- Full AF, IS, and electronic aperture; 1.6× crop on every M body.
Fotodiox Pro EF-NEX
released 2018
Canon EF lens → Sony E (incl. FE) body
- 9 body-side contacts
- no firmware updates
- not weather sealed
- no glass — pass-through
- Budget electronic EF-on-Sony adapter; passes electronic aperture and EXIF, supports basic AF on most modern Canon EF and Sigma DG lenses.
- AF is contrast-detect biased on PDAF-capable Sony bodies — markedly slower than the Sigma MC-11 or Metabones EF-E V. Best for portrait, landscape, and other non-tracking work.
- No firmware-update port; what ships in the box is what you get. Adequate as a second adapter or for backup, not as a primary AF path.

Canon EF — flange distance, protocol, and adapter compatibility

Mount specifications

Adapting Canon EF lenses onto other bodies

Adapting other lenses onto a Canon EF body

Adapter SKU teardown

Canon EF-EOS R

Sigma MC-11

Sigma MC-21

Metabones EF-E Mark V

Metabones Speed Booster ULTRA 0.71× EF-E

Viltrox EF-EOS R5 (autofocus EF-to-RF)

Viltrox EF-NEX IV (EF-E)

Fringer EF-FX Pro II

Fringer EF-GFX Pro

Canon EF-EOS M

Fotodiox Pro EF-NEX

References

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