Viltrox · Canon EF → Micro Four Thirds adapter
Viltrox EF-M2 II — Canon EF → Micro Four Thirds adapter
0.71× focal-reducer ('speed booster') for Canon EF / EF-S glass on Micro Four Thirds bodies — recovers roughly one stop of light and widens the field of view, pulling the effective crop from the bare 2.0× MFT factor toward ~1.42×.
At a glance
- Vendor
- Viltrox
- Release year
- 2018
- Body-side contacts
- 11 pins
- Flags
- firmware-updatableweather-sealed —requires glass
What this adapter preserves
Compatibility for Canon EF lens on a Micro Four Thirds body (computed from the lensmount dataset — open the Canon EF to Micro Four Thirds adapter page for the full verdict, flange clearance, and adapter caveats).
- Focus: Partial AF
- IS: IS / IBIS preserved
- Aperture: Electronic aperture
- Infinity focus: Reaches infinity
Format note: Lens covers full-frame; body is MFT — 2× crop factor applies relative to the lens's native image circle. No vignetting; the body uses the centre of the lens.
What it does
Autofocus supported for EF / EF-S lenses (single-shot AF reliable; continuous AF noticeably slower than native MFT glass). Forwards electronic aperture and EXIF; firmware-updatable via micro-USB.
A Canon EF 50 mm f/1.8 behaves close to a 71 mm f/1.3-equivalent in full-frame field-of-view + depth-of-field terms on the 2× sensor; an EF 24 mm f/2.8 widens to roughly a 34 mm f/2.0-equivalent.
Firmware history
Firmware history
- v1.00
- Initial release of the revised 'II' — improved AF firmware and coatings over the original EF-M2
- 0.71× focal reduction with single-shot AF, electronic aperture, EXIF and in-lens IS pass-through for Canon EF / EF-S glass on Micro Four Thirds bodies, updatable over micro-USB
- v2.00
- AF-tuning refinements and an expanded EF / EF-S + Sigma / Tamron EF lens-compatibility list
- More reliable single-shot AF on Panasonic GH5 / G9 and Olympus OM-D E-M1 Mark II bodies
Approximate milestones — verify against the Viltrox firmware page for the authoritative changelog.
Specific lens compatibility
Per-lens notes for the Viltrox EF-M2 II based on the vendor's published compatibility chart and community-tested behaviour. Three states: works (✓) — full AF / IS / aperture behave as native; partial (⚠) — usable with a documented caveat; issue (✗) — known incompatibility or rough edge.
| Lens | Status | Note |
|---|---|---|
| Canon EF 50 mm f/1.8 STM | Works | STM focus motor drives smoothly for single-shot AF; with the 0.71× reduction it frames like a ~71 mm f/1.3-equivalent on MFT — a natural fast portrait length. |
| Canon EF 70-200 mm f/2.8L IS II USM | Partial | Mounts and shoots with IS and electronic aperture, but it is heavy on an MFT body and continuous-AF tracking lags native glass. Best on a tripod for stills; the reducer widens it toward a ~99-284 mm f/2.0-equivalent reach. |
Try your lens through this focal reducer
Pick a lens focal length, max aperture, target body sensor format, and reducer family below — the calc returns the effective focal length, effective f-number, and full-frame equivalent angle of view on that body. Both focal length and f-number scale by the reducer ratio (so the lens always gets two stops faster, distributed as −2·log₂(ratio) stops).
Speed Booster equivalence calculator
Plug in any Canon EF lens and pick the focal-reducer family. The calc returns the effective focal length and aperture on a APS-C body of your choice, plus the full-frame equivalent angle of view after the body's crop stacks on top.
- Effective focal length
- 35.5 mm
- Effective aperture
- f/1.28
- Full-frame equiv. angle of view
- 53.3 mm
50.0 mm × 0.71 on the reducer.
0.99 stops brighter than f/1.80.
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.
Common questions
- Does the Viltrox EF-M2 II autofocus Canon EF lenses on a Panasonic / Olympus MFT body?
- Yes for single-shot AF with most EF / EF-S lenses; continuous AF and tracking are slower and less reliable than native MFT glass, and performance varies by lens and body. Treat it as a stills focal-reducer rather than a sports / video AF solution.
- What does the 0.71× speed booster actually change?
- It compresses the EF lens's full-frame image circle to better fill the smaller MFT sensor, gaining about one stop of light and widening the field of view. The net effect is an effective crop near 1.42× instead of the bare 2.0× MFT crop — so EF lenses behave more like they would on a larger sensor.
- EF-M2 II vs the original Viltrox EF-M2 — which is which?
- The 'II' is the revised version with improved AF firmware and coatings over the original EF-M2. Both are 0.71× EF → MFT focal reducers with a micro-USB firmware port; the II is the one to buy for the better AF tuning.
Mounts on either side
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- Sigma MC-11 — onto Sony E · 2016
- Sigma MC-21 — onto L-Mount · 2019
- Metabones EF-E Mark V — onto Sony E · 2017
- Metabones Speed Booster ULTRA 0.71× EF-E — onto Sony E · 2014
- Viltrox EF-EOS R5 (autofocus EF-to-RF) — onto Canon RF · 2024
- Viltrox EF-NEX IV (EF-E) — onto Sony E · 2018
- Fringer EF-FX Pro II — onto Fujifilm X · 2020
- Fringer EF-GFX Pro — onto Fujifilm GFX · 2019
- Canon EF-EOS M — onto Canon EF-M · 2012
- Fotodiox Pro EF-NEX — onto Sony E · 2018
- Kipon Baveyes EF-FE 0.7x — onto Sony E · 2017
- Kipon Baveyes EF-FX 0.7x — onto Fujifilm X · 2017
- Commlite CM-EF-NEX HS — onto Sony E · 2018
- Commlite CM-EF-EOS R — onto Canon RF · 2019
- Fotodiox Vizelex ND Throttle EF-NEX — onto Sony E · 2014
- Fringer EF-NZ II — onto Nikon Z · 2023
Same body-side mount (Micro Four Thirds)
- Kipon Baveyes M42-MFT 0.7x — from M42 · 2016
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