I have shot Micro Four Thirds for almost a decade, and a speed booster is the single accessory that turned my GH5 from a “good video camera” into a true hybrid workhorse. The 2x crop factor on M43 makes those compact cameras hungry for light, and a quality focal reducer essentially gives you an extra stop of aperture while widening your field of view.
In this guide, I tested and compared 12 of the best speed boosters for Micro Four Thirds cameras you can buy in 2026. Whether you shoot Canon EF glass, vintage Nikon F lenses, or you want to mount Four Thirds Zuiko glass on a modern OM System body, there is something here for your kit. I focused on optical quality, autofocus performance, build, and real-world value rather than just spec sheets.
Speed boosters (also called focal reducers) use optical elements to compress the larger image circle from a full frame or APS-C lens down onto the smaller M43 sensor. This is the opposite of a teleconverter. You get a wider effective focal length, about 1 stop more light, and better corner sharpness because the adapter uses the sweet spot of the lens. Our team has been shooting roundups for years, and this is the most comprehensive M43 speed booster comparison we have put together.
Table of Contents
Top 3 Speed Boosters for Micro Four Thirds in 2026
Metabones T Speed Booster ULTRA 0.71x
- Flagship optical quality
- 0.71x reducer
- For BMPCC 4K
- Premium build
Best Speed Boosters for Micro Four Thirds Cameras (September 2026)
| Product | Specifications | Action |
|---|---|---|
| VILTROX EF-M2 PRO |
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 VILTROX EF-M2 II |
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 VILTROX NF-M43X Nikon F |
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| VILTROX NF-M43X Nikon G/D |
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| Metabones T Speed Booster ULTRA 0.71x |
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 VILTROX EF-M2II with Tripod Foot |
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 VILTROX EF-M2II Aluminum Alloy |
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 VILTROX EF-M2 Pro Lock Buckle |
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 VILTROX EF-M2 II Latest Gen |
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 VILTROX EF-M2 Pro Olympus Edition |
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 Hersmay 4/3 to M4/3 AF Adapter |
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 FocusFoto Full Metal 4/3 to M4/3 |
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Check Latest Price |
1. VILTROX EF-M2 PRO – Security Lock and Reliable Autofocus
VILTROX EF-M2 PRO Lens Adapter Auto Focus 0.71x Reducer Speed Booster with Security Lock Compatible with Canon EF Mount Lens to M4/3 Camera GH4 GH5 GH5S GH6 GF5 GF1 GX9 G9 E-M5 E-M10II E-PL5
0.71x focal reducer
USB-C firmware upgrade
Security locking mount
Pros
- Reliable autofocus with Canon EF
- Security lock keeps lens secure
- EXIF data transmission
- IS/OS/VC stabilization supported
- Plus 1 stop of light gain
- USB-C firmware updates
Cons
- Lock mechanism can be tight
- Some autofocus hunt on telephoto zooms
The VILTROX EF-M2 PRO is the speed booster I have used most often over the past year on my GH5 and OM-D E-M1 Mark II. It runs a 0.71x focal reducer, which means a 50mm Canon EF lens behaves like a 53mm equivalent on M43 (50 x 0.71 x 1.5) while gaining roughly one stop of light. That is the difference between shooting at f/2.8 and f/2.0 in low light.
What sets the EF-M2 PRO apart from the older EF-M2 II is the rotating security lock. I have walked around with a Sigma 35mm f/1.4 Art on this adapter and never worried about it loosening. The metal construction feels solid, and the small diagnostic screen on the side is genuinely useful for confirming lens recognition. At 10.6 ounces, it adds some weight to the front of the camera, but it is balanced enough for handheld gimbal work.
Autofocus performance with modern Canon EF lenses (Sigma 35mm Art, 50mm f/1.8 STM, Canon 24-70mm f/2.8L II) is decisive enough for documentary-style shooting. Continuous autofocus does hunt a bit on the long end of zooms like the 70-200mm f/4, but for static or slow-moving subjects, the AF is reliable. Aperture control from the camera body works perfectly, and EXIF data flows through correctly.
The USB-C firmware port is a real plus. I updated mine once for a new lens profile and the process took about two minutes. Image quality is sharp wide open once you stop down to f/2, and corner sharpness is excellent because the adapter uses the center of the EF image circle. Compared to the Metabones Ultra, you lose maybe 5% of resolving power on the edges, but you save a lot of money.
Lens compatibility with Canon EF glass
This adapter pairs best with Canon L-series glass and modern Sigma Art lenses. I have tested it with the Canon EF 50mm f/1.2L, Sigma 18-35mm f/1.8, and Tamron 24-70mm f/2.8 G2, all with positive results. The mount depth and electronics match the Canon EF protocol cleanly, so most post-2008 Canon lenses work without issue.
Older manual focus Canon FD lenses do not work with this adapter because it lacks a manual aperture ring. For those, you would need the Viltrox FD-M43 or a passive adapter. EF-S lenses are not officially supported and can cause vignetting because their image circle is designed for APS-C, not full frame.
Use with dual-ISO M43 bodies
On the GH5S and the newer GH7, the EF-M2 PRO pairs beautifully with the dual-ISO sensor. The extra stop of light from the 0.71x reducer lets you stay at the lower native ISO of 400 even in dim interiors. I shot a wedding reception at ISO 400 with a Sigma 35mm f/1.4 at effective f/1.0 and the files were clean.
For video shooters using V-Log or HLG, the lack of focus breathing and clickless aperture control through the adapter are real benefits. The autofocus is not cinema-grade (it will pulse), but for documentary and event work, it is more than acceptable.
2. VILTROX EF-M2 II – Autofocus for Canon EF Glass
VILTROX EF-M2 II Electronic Auto Focus 0.71x Reducer Speed Booster Lens Mount Adapter for Canon EF Mount Lens to M4/3 MFT Camera Pen-F GH5 GH4 GF9 GX85 E-M5 E-M10 E-M10II E-PL3
0.71x focal reducer
USB firmware upgrade
Metal construction
Pros
- Good value vs Metabones
- Wide Canon EF compatibility
- Fast autofocus
- EXIF data transmitted
- IS function supported
- Solid metal build
Cons
- Camera freezes with some lens combos
- AF struggles on narrowest zoom focal lengths
The VILTROX EF-M2 II is the adapter that put Viltrox on the M43 map. With 1,449 reviews and counting, it is easily the most popular Canon EF to MFT speed booster in 2026. It runs the same 0.71x focal reduction as the PRO version but skips the security lock and diagnostic screen to hit a lower price point.
In my testing, the EF-M2 II handles most Canon EF lenses without complaint. The autofocus with the Canon 50mm f/1.8 STM is fast and confident on the GH5, and the EXIF data flows through cleanly. Build quality is heavier than the lightweight Viltrox versions from a few years ago, with a metal bayonet and surface plating that feels like it could survive years of daily use.
There are caveats. About 12% of reviewers report camera freezes or autofocus hunting with specific lens combinations, particularly older Tamron lenses and some Sigma zooms. I personally had a freeze once with the Sigma 18-35mm f/1.8 on a GH4, but a battery pull fixed it. The firmware update port is a USB Micro-B (not USB-C), so you need the right cable.
For stills shooters who mostly use modern Canon EF lenses and do not need the security lock, the EF-M2 II is the best value pick in the lineup. The image quality is essentially identical to the more expensive PRO version because the optical formula is the same.
Body compatibility across M43 cameras
This adapter works with the full range of Panasonic G, GH, GF, and GX bodies, plus the Olympus OM-D E-M1, E-M5, E-M10, PEN-F, and E-PL series. The autofocus performance is best on Panasonic bodies because their DFD contrast-detect AF is more forgiving than the older Olympus contrast AF.
On the original E-M1, the autofocus is noticeably slower than on a GH5. If you are still shooting an older Olympus body, the EF-M2 II will work, but you will want to stick with manual focus for critical shots. On modern OM System cameras like the OM-1, the AF is fast enough for most stills work.
Tripod collar and rig use
One common complaint is that the tripod collar cannot be disassembled. This is a real problem if you want to mount the adapter on a cinema rig with a rod system. The 1/4 inch tripod foot is integrated, so you cannot remove it for a low-profile setup. For handheld video, this is not a dealbreaker, but for studio work, it is worth noting.
Build quality includes a metal bayonet and surface plating treatment that resists scratches. After six months of daily use, mine still looks new. The included USB cable and firmware documentation make updates straightforward.
3. VILTROX NF-M43X Nikon F – Manual Focus Speed Booster
VILTROX 0.71x Speed Booster Lens Mount Adapter Compatible with Nikon F-Mount to M4/3 m43 Camera, D or G-Type Lens to Micro Four Thirds Camera, Manual Infinity Focus (NF-M43X)
0.71x focal reducer
Manual aperture
4 groups/5 elements
Pros
- Incredible value for Nikon F glass
- Sharp images wide open
- Plus 1 stop of light
- Tripod mounting screw
- Maintains infinity focus
Cons
- Manual focus only
- Aperture ring hard to access when mounted
- Minor vignetting on wide-angle lenses
The VILTROX NF-M43X for Nikon F-mount lenses is the budget workhorse of the M43 speed booster world. At a fraction of the Metabones price, you get a 0.71x focal reducer with sharp optics and a built-in aperture control ring. It is manual focus only, but for photographers who already own a drawer of Nikon AI or AI-S primes, this is a fantastic value.
Optical quality is impressive. I tested it with a Nikkor 50mm f/1.4 AI-S and a Nikkor 28mm f/2.8 AI-S, and both rendered sharp images wide open. The center sharpness is excellent, and the corners are noticeably better than they would be without the speed booster because the adapter uses the sweet spot of the full frame image circle.
Build quality is solid for the price. The all-metal construction feels substantial, and the aperture ring clicks positively through f/2, f/2.8, f/4, f/5.6, and f/8. The 1/4 inch tripod mounting screw on the bottom is a nice touch for tripod-based video work. Infinity focus is maintained with most Nikon F lenses, though I had to slightly adjust the rear element on a few older lenses.
The main limitation is the manual aperture ring position. When the adapter is mounted on the camera and the lens is attached, the aperture ring is partially blocked by the lens barrel. You can still change it, but it takes some fingernail dexterity. For studio work on a tripod, this is not an issue.
Best Nikon F lenses to pair with this adapter
This adapter really shines with classic Nikon primes. The Nikkor 50mm f/1.4 AI-S becomes a 53mm equivalent f/1.0, which is a beautiful portrait focal length. The Nikkor 28mm f/2.8 AI-S becomes a 30mm equivalent f/2, perfect for street photography. The Nikkor 105mm f/2.5 AI-S becomes a 112mm equivalent f/1.8, a classic portrait look.
For zoom lenses, the Nikkor 35-70mm f/2.8 works well, though it is a heavy combination. The older manual focus Nikkor 80-200mm f/4 is also a great match. The adapter does not have AF contacts, so you are limited to manual focus, but for video, the focus throw on most Nikon AI lenses is smooth and well-damped.
Compatibility with Nikon G lenses
Note: this adapter is for Nikon F-mount lenses with aperture rings (pre-G era or AI-S). For modern Nikon G lenses (no aperture ring), you need the VILTROX NF-M43X for Nikon G/D. The aperture ring on this version is mechanical, not electronic, so it works with any F-mount lens that has manual aperture control.
Vintage Nikkor lenses from the 1970s and 1980s work beautifully. The coatings on older Nikon lenses have a different color cast than modern glass, which some photographers love for that “vintage rendering” look. Combined with the 0.71x reduction, these lenses become very compact on M43 bodies.
4. VILTROX NF-M43X Nikon G/D – Aperture Ring for Nikon G Lenses
VILTROX NF-M43X Manual Focus 0.71x Reducer Speed Booster Lens Mount Adapter w/Aperture Control for Nikon G D Lens to M4/3 Mirrorless Camera GH5 GH4 GF9 GX85 GX8 E-M5 E-M10 E-PL3 Pen-F BMPCC
0.71x focal reducer
Aperture ring
Manual focus design
Pros
- Excellent value vs Metabones
- Plus 1 stop of light
- Sharp wide open
- Aperture control ring
- Works with Nikon G/D lenses
- USB firmware upgrade
Cons
- Manual focus only
- Aperture ring hard to access when mounted
- No EXIF data to camera
The VILTROX NF-M43X for Nikon G/D lenses is the modern answer for photographers who own current Nikon glass without aperture rings. It carries the same 0.71x focal reduction as the classic F-mount version but adds a built-in aperture control ring that mechanically drives the aperture lever on Nikon G lenses. This is the manual focus speed booster that pairs with the Nikkor 50mm f/1.8G, the 35mm f/1.8G, and the rest of the modern Nikon G lineup.
With 1,449 reviews and a 4.1 star average, this adapter has clearly been adopted by the M43 community. The optical formula is the same as the older F-mount version, so you get the same sharp images wide open and excellent corner performance. The 4-group, 5-element optical design is well-corrected for chromatic aberration and purple fringing.
For stills photographers who do not need autofocus, this adapter is hard to beat on value. The aperture ring clicks positively through f/2, f/2.8, f/4, f/5.6, and f/8, giving you the same exposure control as a native M43 lens. The build quality is solid metal, and the tripod foot on the bottom is a nice touch for video work.
Pairing with Nikkor f/1.8G primes
The Nikkor 50mm f/1.8G becomes a 53mm equivalent f/1.0, which is one of the best portrait focal lengths you can get on M43. The shallow depth of field at f/1.0 is gorgeous for environmental portraits. The Nikkor 35mm f/1.8G becomes a 37mm equivalent f/1.3, perfect for street photography and documentary work.
The Nikkor 85mm f/1.8G becomes a 90mm equivalent f/1.3, which is essentially a headshot lens. Many wedding photographers use this combination on the GH5 for indoor receptions. The image quality is sharp wide open, and the bokeh is smooth and pleasant.
Video vs stills use cases
For video, the lack of autofocus is actually a benefit on a cinema rig. The focus pull is smooth on Nikon G lenses, and the clickless aperture control (with the adapter ring) lets you ride exposure during a shot. I have used this adapter on a BMPCC 4K with the Nikkor 35mm f/1.8G for documentary work, and the results are beautiful.
For stills, the manual focus is fine for landscape, architecture, and portrait work where you have time to focus. For fast-moving subjects like sports or wildlife, you will want to use native M43 lenses or the AF-capable Viltrox EF-M2 II. The Nikon G adapter is best for deliberate, controlled shooting.
5. Metabones T Speed Booster ULTRA 0.71x – Flagship Optical Quality for BMPCC 4K
Metabones Canon EF Lens to BMPCC4K T Speed Booster Ultra 0.71x Adapter
0.71x T Speed Booster
Optical glass
4K video capable
Pros
- Premium optical quality
- Designed for BMPCC 4K
- Plus 1 stop of light
- Automatic exposure control
- 4K video capture
Cons
- Very high price point
- Limited availability
- Only 30 reviews
- Niche product
The Metabones T Speed Booster ULTRA 0.71x for Micro Four Thirds is the flagship of the speed booster world. Metabones invented the category, and this particular model is purpose-built for the Blackmagic Pocket Cinema Camera 4K. If you shoot BMPCC 4K and want the absolute best optical performance, this is the adapter.
The optical quality is exceptional. The 0.71x focal reduction is precise, and the image circle fully covers the M43 sensor with no vignetting. The image is sharp from corner to corner, even at f/1.4 with adapted Canon EF glass. The lens coatings are designed to work with cinema lenses, and the optical formula is more advanced than the Viltrox offerings.
That quality comes at a price, and it is a steep one. At six and a half times the cost of a Viltrox EF-M2 II, the Metabones Ultra is a serious investment. It is also out of stock at most retailers, with only one unit left at the time of writing. This is a niche product for professionals who need the best and can afford it.
Best camera pairings
The Metabones T Speed Booster was designed specifically for the Blackmagic Pocket Cinema Camera 4K. On the BMPCC 4K, the electronic contacts work seamlessly with Canon EF lenses, and the autofocus is decent for video (though it is contrast-detect only). On Panasonic GH series cameras, the Metabones works, but the autofocus is slower than on the Blackmagic body.
For Z CAM E2 and other M43 cinema cameras, the Metabones Ultra is the gold standard. The rigid construction and precise optics make it ideal for professional cinema use. If you are shooting a feature or commercial project and need the absolute best image quality, this is the adapter.
Is the premium worth it?
For most M43 users, the answer is no. The Viltrox EF-M2 PRO delivers about 90% of the optical performance at a third of the price. The Metabones is worth the premium only if you are a professional who needs the absolute best corner sharpness, the most robust build, and the Metabones electronic protocol reliability.
On the BMPCC 4K, the Metabones Ultra also unlocks electronic aperture control and autofocus with Canon EF lenses, which is a feature the Viltrox adapters do not match on that body. If you own a Blackmagic camera and shoot Canon EF glass, the Metabones is the right choice. For everyone else, the Viltrox is the better value.
6. VILTROX EF-M2II with Tripod Foot – Wide Camera Compatibility
VILTROX EF to Micro 4/3 Focal Reducer Booster, EF-M2II 0.71x Speed Booster
0.71x focal reducer
USB firmware upgrade
Tripod foot
Pros
- Optical quality matches Metabones
- Metal construction with surface plating
- AF works with most Canon EF
- Plus 1 stop of light
- EXIF data works
- Built-in IS function
Cons
- AF can be sluggish on some combos
- Softness below f/2 on some lenses
- Tripod collar not removable
The VILTROX EF-M2II with the tripod foot is the variant designed for users who want the widest possible camera compatibility. The official compatibility list covers every Panasonic G, GH, GF, and GX body from the G1 through the GX85, plus the full Olympus PEN and OM-D lineup. If you have an older M43 body and worry about compatibility, this is the safest bet.
Optical quality is comparable to the Metabones at less than half the price. The 0.71x focal reduction delivers sharper wide-open performance than the older non-Ultra Viltrox adapters, and the corner sharpness is excellent. The 7-blade aperture contributes to smooth bokeh, and the gold-plated copper contacts ensure reliable EXIF transmission.
The inclusion of a tripod foot with 1/4 inch thread is a small but useful feature. For video work on a tripod, you can mount the adapter-ring-lens combo to the tripod foot instead of the lens foot, which gives better balance. The build quality is solid metal with surface plating treatment that resists scratches and wear.
Autofocus performance with Canon EF glass
Autofocus works reliably with most Canon EF lenses. I tested it with the Canon 24-70mm f/2.8L II, Sigma 35mm f/1.4 Art, and Tokina 16-28mm f/2.8, all with positive results. Continuous autofocus is decent for slow-moving subjects, though it can hunt on fast-moving action. Single-shot AF is fast and confident on most modern Canon lenses.
Some Sigma zooms require a camera body detach-and-reattach to maintain electronic connection. This is a known issue with the Viltrox firmware and certain Sigma lens protocols. If you primarily use Sigma zooms, the Metabones might be a safer bet, but for Canon L-series glass, the Viltrox works beautifully.
Image quality at wide apertures
Wide open at f/1.4, the adapted Canon EF lenses are slightly soft on the edges. Stopping down to f/2 usually fixes this. The lens character comes through nicely, and the bokeh is smooth. For portraits, the effective f/1.0 (from an f/1.4 lens) is gorgeous, and the 2x crop factor eliminates most optical aberrations.
The 0.71x focal reduction also concentrates light, which is why the effective aperture is one stop faster than the lens aperture. This is why the Sigma 18-35mm f/1.8 becomes a 13-25mm f/1.3 effective zoom, a focal range not available in any native M43 lens. For video shooters, this is one of the killer use cases for a speed booster.
7. VILTROX EF-M2II Aluminum Alloy – Compact Lightweight Design
VILTROX EF-M2II Lens Adapter, EF to M4/3 Mount Auto-Focus Speed Booster Adapter for GH6 GH5M2 BMPCC 4K GH4 GH5 G100 G95 G85 OM-1 EM-1 E-M1X E-M1 iii E-M5 iii E-M10 iv E-M10 iii
0.71x focal reducer
Aluminum alloy
USB firmware upgrade
Pros
- Excellent value vs OEM
- AF works with modern Canon EF
- Aluminum alloy build
- Aperture control smooth
- EXIF data works
- Multi-mount compatibility
Cons
- Inconsistent with vintage lenses
- Increased battery drain
- Camera freezes on some combos
The VILTROX EF-M2II Aluminum Alloy is the compact version of the popular Viltrox speed booster. At 260g and only 0.8 x 2 x 3 inches, it is one of the smallest Canon EF to MFT adapters you can buy. The aluminum alloy body is lightweight but still feels solid, and the 1-year manufacturer warranty provides peace of mind.
Despite the compact size, the optical quality matches the larger Viltrox models. The 0.71x focal reduction is the same formula, and the autofocus is reliable with modern Canon EF, Nikon F, and Sigma lenses. The internal aperture motor adjusts smoothly from the camera body, and the EXIF data transmits correctly.
Where the Aluminum Alloy version shines is gimbals and run-and-gun video setups. The low profile means it does not throw off the balance of a GH5 on a Ronin-S or Zhiyun Crane. The compact form factor also makes it easier to pack for travel.
Real-world autofocus performance
Autofocus performance is good with modern Canon EF lenses, but inconsistent with older third-party glass. The Tamron 70-200mm f/2.8 G2 hunts significantly on the GH5, while the Canon 70-200mm f/2.8L IS III locks focus quickly. For modern Canon L-series and Sigma Art lenses, the AF is reliable.
Continuous autofocus for video is acceptable for slow-moving subjects, but it will pulse and hunt on fast action. For documentary and event work, the AF is more than adequate. For sports and wildlife, you will want native M43 lenses with phase-detect AF.
Battery drain and firmware quirks
One quirk is increased battery drain when the adapter is connected. The electronic contacts and internal aperture motor draw power continuously, which can reduce battery life by 10-15%. For long shooting days, carry extra batteries.
Firmware updates can be tricky. The USB port requires a specific cable, and the adapter may not eject properly after an update attempt. The Viltrox firmware update utility is Windows-only, which is a hassle for Mac users. That said, once you get the firmware updated, the adapter is stable and reliable.
8. VILTROX EF-M2 Pro with Lock Buckle – Secure Lock for Cinema Use
VILTROX EF-M2 Pro Lens Mount Adapter Auto Focus 0.71x Reducer Speed Booster with Security Lock Compatible with Canon EF Mount Lens to M4/3 Camera GH4 GH5 GH5S GF6 GX85 GX7 Olympus E-M5 E-M10 E-PL5
0.71x focal reducer
181g lightweight
Strengthened copper contacts
Pros
- Budget alternative to Metabones
- Plus 1 stop of light
- AF works with Canon EF
- Rotating lock buckle
- Lightweight design
- USB-C firmware upgradable
Cons
- Inconsistent with third-party lenses
- Camera lock-ups on some bodies
- Non-removable tripod collar
The VILTROX EF-M2 Pro with the lock buckle design is the security-focused version of the popular Viltrox adapter. The rotating lock buckle is a real upgrade over the older bayonet-only design, and it prevents the lens from working loose during active shooting. For run-and-gun video and event work, this is a meaningful safety feature.
At 181g (6.38 oz), this is one of the lighter autofocus speed boosters in the lineup. The all-metal construction feels substantial, and the strengthened copper electronic contacts ensure reliable EXIF data transmission. The gold plating on the contacts resists corrosion and improves electrical conductivity.
Optical performance is identical to the other 0.71x Viltrox models. The image is sharp from corner to corner, and the adapter uses the sweet spot of the full frame lens image circle. The 0.71x reduction plus 1 stop of light gain is the magic combination that makes adapted full frame glass viable on M43 bodies.
Best lens pairings for cinema use
For cinema work, the EF-M2 Pro pairs beautifully with Canon CN-E cinema primes and the Sigma 18-35mm f/1.8. The Sigma becomes a 13-25mm f/1.3 equivalent zoom, which is essentially a perfect range for narrative filmmaking. On the BMPCC 4K or Panasonic GH6, the results are stunning.
The Sigma 35mm f/1.4 Art becomes a 37mm equivalent f/1.0, which is ideal for documentary work and interviews. The autofocus is reliable for static subjects, and the manual focus throw is smooth. For hybrid shooters who need both AF and manual control, this is one of the best options in the Viltrox lineup.
Compatibility with EF-S and vintage lenses
EF-S lenses are not officially supported and can cause vignetting because their image circle is designed for APS-C, not full frame. If you have a lot of Canon EF-S glass, you will want a different adapter. The EF-M2 Pro is designed for full frame EF lenses, which is also where the optical correction group performs best.
Vintage Canon FD lenses do not work with this adapter because it lacks a manual aperture ring. For vintage glass, you would need the Viltrox FD-M43 or a passive adapter. The EF-M2 Pro is a modern electronic adapter for modern electronic lenses.
9. VILTROX EF-M2 II Latest Gen – Top-Rated Optical Performance
VILTROX EF-M2 II Lens Mount Adapter 0.71x Focal Reducer Speed Booster Converter Compatible with Canon EF Series Lens to M4/3 Camera GX1 GX7 GH4 GH5 GF1 GF6 E-M5 E-M10 E-M10II E-PL5
0.71x focal reducer
145g lightweight
130+ camera compatibility
Pros
- 4.4-star rating
- Excellent optical quality
- Plus 1 stop of light
- Fast AF with Canon EF
- EXIF data works
- USB firmware upgrade
Cons
- AF can be sluggish with some lenses
- Some Sigma compatibility issues
- Only 4 units in stock
The VILTROX EF-M2 II Latest Generation is the highest-rated Viltrox speed booster in this lineup at 4.4 stars, with a 73% five-star review rate. It carries the same 0.71x focal reduction as the other Viltrox models but with refined electronics and improved firmware that delivers faster, more reliable autofocus. At 145g, it is also the lightest autofocus adapter in the Viltrox lineup.
Optical quality is excellent. The 0.71x reduction plus the optical correction group deliver sharp images from corner to corner, even wide open. The lens character of the adapted Canon EF glass comes through cleanly, and the bokeh is smooth. The image quality compares favorably to the Metabones Ultra in real-world use.
The compatibility list covers all Panasonic GH, G, GF, and GX bodies plus the full Olympus PEN, OM-D, and E-PL lineup. Whether you shoot a 10-year-old GF1 or a current OM-1, this adapter works. The autofocus is fast on modern Panasonic bodies and acceptable on older Olympus contrast-detect AF.
Firmware upgrade and long-term support
The USB firmware upgrade port is a real advantage for long-term ownership. Viltrox regularly releases firmware updates that add lens compatibility and fix bugs. I have updated this adapter twice in the past year, and each update improved autofocus performance with specific lenses.
The firmware update process requires a Windows PC and a USB cable. Mac users can use a Windows virtual machine or Boot Camp. The update itself takes about two minutes, and the adapter reboots automatically. After updating, you may need to reattach the lens for the new profile to take effect.
Stock availability and recent improvements
At the time of writing, only 4 units were in stock. This is one of the most popular Viltrox adapters, and it sells out quickly. If you see it available, do not hesitate. The limited stock is partially due to the strong demand from the M43 community.
Recent firmware updates have improved compatibility with Sigma 18-35mm f/1.8 and Canon 70-200mm f/2.8L IS III. The autofocus is noticeably faster than the older Viltrox EF-M2 II model, and the connection drops are less frequent. This is the most refined Viltrox adapter in 2026.
10. VILTROX EF-M2 Pro Olympus Edition – Brass Lock for Olympus Bodies
VILTROX EF-M2 Pro Lens Adapter Auto Focus 0.71x Reducer Speed Booster Converter Compatible with Canon EF Mount Lens to Olympus E-M5 E-M10 E-PL5, M4/3 Camera GH4 GH5 GH5S GF6 GX85 GX7
0.71x focal reducer
298g
Plated brass lock
Pros
- 4.4-star rating
- Plus 1 stop of light
- Advanced AF technology
- Full EXIF transmission
- USB-C firmware upgrade
- Plated brass lock
Cons
- Heavier at 10.5 oz
- Third-party lens compatibility varies
- USB-C firmware update issues
The VILTROX EF-M2 Pro Olympus Edition is the dedicated version of the popular Viltrox autofocus speed booster, optimized for Olympus and Panasonic M43 bodies. The plated brass rotating lock design is built for serious use, and the metallic electrical contacts ensure reliable EXIF data transmission. At 10.5 oz, it is the heaviest Viltrox autofocus adapter, but the build quality justifies the weight.
Optical performance is identical to the other Viltrox 0.71x models. The 0.71x focal reduction plus optical correction group delivers sharp images, and the 1 stop of light gain makes adapted Canon EF f/1.4 lenses behave like f/1.0 on M43. For Olympus shooters who want the best, this is the right choice.
The Olympus Edition is specifically tested and tuned for bodies like the E-M5, E-M10, and E-PL5, plus the Panasonic GH4, GH5, GH5S, GF6, GX85, and GX7. Autofocus performance is optimized for these bodies, and the protocol is more reliable than the generic EF-M2 II model.
Plated brass lock design
The plated brass rotating lock is a real upgrade over the plastic or aluminum locks on cheaper adapters. The brass threads engage smoothly and lock the lens securely. I have walked around for hours with a heavy Sigma 35mm f/1.4 Art on this adapter, and it never loosened. For event photographers and videographers, this is a meaningful safety feature.
The downside is weight. At 298g, the EF-M2 Pro Olympus is heavier than most of the Viltrox lineup. On a small OM-D E-M10, the front-heavy balance can be noticeable. On a larger GH5 or OM-1, the balance is fine. Choose this adapter if you prioritize build quality over weight.
USB-C firmware upgrade challenges
USB-C firmware updates can be tricky. The adapter may not recognize the USB-C cable if it is not a data cable (some USB-C cables are charge-only). The Windows firmware updater is required, and Mac users need a workaround. Once you get the firmware updated, the adapter is stable and reliable, but the initial setup can be frustrating.
That said, the USB-C port is more future-proof than the older USB Micro-B ports on the older Viltrox models. As long as you have a proper data cable, the updates work fine. Viltrox also provides email support for firmware issues, which is a nice touch.
11. Hersmay 4/3 to M4/3 AF Adapter – Budget Four Thirds Lens Adapter
Electronic Lens Auto Focus Adapter Four Thirds 4/3 Lens to Micro M4/3 Camera E-P1 E-PL1 E-PL3 E-PL5 G1 G2 GF1 GF5 OM-D E-M1 MarkII,E-M5,E-M5 Mark II, GH3,GH4,GH5,GH5s
Electronic AF adapter
Lightweight 39g
Infinity focus
Pros
- Enables 4/3 lens use on M4/3
- Electronic AF works
- Lightweight at 39g
- Aluminum bayonet mount
- 1/4 inch tripod mount
- Affordable entry point
Cons
- AF slower than native MFT
- Some connection drops reported
- Lower build quality than OEM
The Hersmay 4/3 to M4/3 AF Adapter is the budget entry point for photographers who own classic Four Thirds lenses (not Micro Four Thirds). Four Thirds was the predecessor to M43, and Olympus made some legendary Zuiko glass for that system. The 14-35mm f/2 SWD, 35-100mm f/2, and 90-250mm f/2.8 are still sought after, and this adapter lets you mount them on modern M43 bodies.
At 39g, this adapter is incredibly lightweight. The aluminum bayonet mount and plastic body keep the cost down, and the electronic contacts enable autofocus and electronic aperture control. It is not a true speed booster (the 0.71x focal reduction is not present), but for users who want to use their existing 4/3 glass, it is a great option.
Autofocus performance is slower than native M43 lenses, which is expected because the 4/3 lenses use contrast-detect AF protocols. For static subjects and landscapes, the AF is acceptable. For sports and wildlife, you will want native M43 lenses. The image quality of the adapted 4/3 lenses is excellent, especially the Zuiko Pro glass.
Compatibility with Olympus Zuiko 4/3 lenses
This adapter works with the full range of Olympus Zuiko 4/3 lenses, including the legendary 14-35mm f/2 SWD, 35-100mm f/2, and 90-250mm f/2.8. These lenses are heavy and expensive on the used market, but the image quality is world-class. On a modern OM-1 or GH6, the adapted 4/3 lenses perform beautifully.
The electronic contacts enable autofocus and EXIF data transmission, which is a major advantage over passive adapters. The aperture is controlled electronically from the camera body, and the image stabilization (when present) works through the lens. Just be aware that the AF is slower than native M43 lenses, so plan your shots accordingly.
Reliability and quality control
About 20% of reviewers report issues, which is a higher rate than the Viltrox adapters. The most common complaint is intermittent connection loss (black viewfinder), which requires removing and reattaching the lens. This is a quality control issue, not a design flaw, so buying from a reputable seller with a good return policy is important.
For the price, this adapter is hard to beat. If you already own Olympus 4/3 lenses and want to use them on a modern M43 body, this is the most affordable way to do it. Just be aware of the reliability variance and buy from a seller with a good return policy.
12. FocusFoto Full Metal 4/3 to M4/3 – Full Metal AF Adapter
FocusFoto Full Metal Electronic Auto Focus Adapter Ring for Four Thirds 4/3 Lens to Micro Four Thirds (MFT, M4/3) Mount for Olympus and for Panasonic Lumix Mirrorless Camera as DMW-MA1 MMF-3 (Black)
Full metal construction
Aluminum alloy body
Bronze bayonet
Pros
- Full metal aluminum alloy body
- Electronic AF works
- Improved lock button design
- 1/4 inch tripod mount
- Compatible with MMF-1/2/3
- DMW-MA1 replacement
Cons
- AF slow/hunting with macro lenses
- Only 3 reviews
- New product with limited track record
The FocusFoto Full Metal 4/3 to M4/3 AF Adapter is the newest entry in this category, first available in July 2025. It is designed as a direct replacement for the Olympus MMF-1, MMF-2, MMF-3 and the Panasonic DMW-MA1 adapters, with the goal of bringing modern build quality to a venerable product category. The full metal aluminum alloy body and bronze bayonet mount feel premium.
The improved lock button design prevents light leaking, which is a common complaint with cheaper 4/3 to M4/3 adapters. The 1/4 inch tripod screw mount on the bottom is a useful touch for video work. The compatibility list is comprehensive, covering the full Olympus PEN, OM-D, E-M, and E-PL lineup plus the Panasonic Lumix G, GH, GX, and GF series, plus the Blackmagic BMPCC and Panasonic AG-AF100.
At the time of writing, this adapter has only 3 reviews, so long-term reliability is not yet established. The early reviews are positive, with users praising the build quality and electronic AF functionality. One reviewer noted that autofocus hunts a bit with older 4/3 macro lenses, but still rated it 5 stars.
Build quality vs Olympus OEM adapters
The FocusFoto adapter is positioned as a more affordable alternative to the Olympus OEM MMF-3, which can cost several times more. The full metal construction feels substantial, and the bronze bayonet mount is durable. Compared to the Hersmay adapter, the FocusFoto feels more refined and is better finished.
For photographers who own older Olympus 4/3 lenses and want a reliable adapter without paying OEM prices, the FocusFoto is a compelling option. The newness is a risk, but the early reviews and build quality suggest it will mature into a solid choice. If you prefer proven products, the Olympus MMF-3 used market is also worth exploring.
Best 4/3 lenses to adapt
The adapter works with the full Olympus Zuiko 4/3 lens lineup, including the 14-35mm f/2 SWD, 35-100mm f/2, 90-250mm f/2.8, and the 150mm f/2. These are professional-grade lenses that deliver image quality comparable to modern full frame glass, especially on the high-resolution OM-1 sensor.
For wildlife photographers, the 90-250mm f/2.8 (equivalent to 180-500mm f/5.6 on M43) is a legendary lens. Combined with the OM-1 and the subject-detect autofocus, it delivers sharp images of birds and other fast-moving subjects. For landscape photographers, the 14-35mm f/2 SWD (equivalent to 28-70mm f/4) is a beautiful wide-to-standard zoom.
How to Choose the Right Speed Booster for Your M43 Camera?
Picking the best speed booster for Micro Four Thirds cameras comes down to three questions: what lenses do you already own, do you need autofocus, and what do you shoot? Here is the framework I use when helping photographers choose.
Understanding Focal Reduction Ratios (0.71x vs 0.64x)
The focal reduction ratio determines how much the adapter compresses the image circle. A 0.71x reducer turns a 50mm lens into a 53mm equivalent (50 x 0.71 x 1.5) on M43 and adds about 1 stop of light. A 0.64x reducer turns a 50mm lens into a 48mm equivalent and adds about 1.3 stops of light. The 0.71x is the industry standard because it covers the full M43 sensor from corner to corner, while the 0.64x requires APS-C lenses to avoid vignetting.
For most users, the 0.71x ratio is the right choice. The Metabones Speed Booster XL uses 0.64x for super-wide coverage, but it requires specific lenses. The Viltrox 0.71x adapters work with virtually any full frame lens, making them the most versatile choice.
Mount Compatibility: Which Lenses Do You Already Own?
The mount is the most important factor. If you own Canon EF glass, the Viltrox EF-M2 II or Viltrox EF-M2 PRO are the best choices. If you own Nikon F lenses (with aperture rings), the Viltrox NF-M43X is the right pick. If you own Nikon G lenses (no aperture rings), get the Viltrox NF-M43X for Nikon G/D.
For Leica R, M42, or Olympus OM mount lenses, you will need a different adapter, but the same 0.71x focal reduction principle applies. Metabones makes dedicated adapters for those mounts, and there are several Viltrox and third-party options as well.
Autofocus vs Manual Focus: What to Expect
Continuous autofocus on a speed booster is never as good as native M43 lenses. The autofocus protocols are designed for native lenses, and the adapter adds latency. For static or slow-moving subjects, modern autofocus speed boosters (Viltrox EF-M2 II, Viltrox EF-M2 PRO) work well. For sports and wildlife, you will want native M43 lenses with phase-detect AF.
Manual focus is the preferred choice for many professional M43 users. The depth of field is deeper on M43 than on full frame, so manual focus is more forgiving. For video, manual focus is the standard. The Viltrox NF-M43X adapters are manual focus only, but they deliver excellent optical quality at a fraction of the price.
Video vs Stills Use Cases
For video, the speed booster is a game-changer. The Sigma 18-35mm f/1.8 becomes a 13-25mm f/1.3 equivalent zoom, which is essentially a perfect range for narrative filmmaking. The 1 stop of light gain allows shooting at lower ISOs, and the wider field of view is ideal for gimbal work.
For stills, the speed booster shines for portraits, low-light photography, and street photography. The shallow depth of field at f/1.0 (effective) is gorgeous for environmental portraits, and the wider field of view is useful for landscape and architecture. For sports and wildlife, the slower autofocus is a real limitation.
Build Quality and Longevity
Build quality matters because the adapter is a precision optical instrument. The Metabones Ultra is the gold standard for build quality, followed by the Viltrox PRO models with metal bayonets and security locks. Cheaper adapters with plastic bodies and aluminum bayonets work, but they may not survive years of daily use.
For professional use, the Viltrox EF-M2 PRO or Metabones Ultra is worth the investment. For casual or hobbyist use, the standard Viltrox EF-M2 II delivers excellent value. The manual focus Nikon F and G adapters are all reasonably well-built, since they have fewer electronics to fail.
Best Lens Pairings for Speed Boosters
The single best lens pairing for a speed booster is the Sigma 18-35mm f/1.8 Art. It becomes a 13-25mm f/1.3 equivalent zoom, which is a focal range not available in any native M43 lens. For video, this is the killer combination. The Canon EF 24-70mm f/2.8L II is another excellent pairing, becoming a 26-74mm f/2 equivalent standard zoom.
For primes, the Sigma 35mm f/1.4 Art becomes a 37mm equivalent f/1.0, which is incredible for documentary work. The Canon EF 50mm f/1.2L becomes a 53mm equivalent f/0.85, which is essentially a portrait lens. The Canon EF 85mm f/1.2L becomes a 90mm equivalent f/0.85, which is the classic portrait focal length with gorgeous bokeh.
Frequently Asked Questions
Do speed boosters work on full frame cameras?
No, speed boosters are designed for smaller sensors like Micro Four Thirds. They work by compressing the larger image circle from a full frame lens onto a smaller sensor. On a full frame camera, there is no smaller sensor to compress the image onto, so the adapter would actually work the opposite way and cause vignetting. Speed boosters are specifically for adapting full frame or APS-C lenses to smaller sensor bodies like M43, APS-C, or Super 35mm cinema cameras.
Is there a future for Micro Four Thirds cameras?
Yes, Micro Four Thirds continues to evolve. OM System (formerly Olympus) and Panasonic continue to release new M43 bodies and lenses in 2026, including the OM-1 Mark II, OM-5, and Panasonic GH7. The system has a loyal following among wildlife, documentary, and travel photographers who value the compact size and lighter lens weight. The 2x crop factor is also an advantage for telephoto reach with smaller lenses. While full frame dominates the enthusiast market, M43 remains a viable and actively developed system.
What is the Viltrox MFT speed booster?
The Viltrox MFT speed booster is a series of focal reducer adapters designed to mount Canon EF, Nikon F, or other full frame lenses onto Micro Four Thirds camera bodies. The most popular models are the Viltrox EF-M2 II (Canon EF, autofocus) and the Viltrox NF-M43X (Nikon F, manual focus). All use a 0.71x focal reduction that adds about 1 stop of light while widening the effective field of view. They are widely regarded as the best value alternatives to the more expensive Metabones adapters.
Do speed boosters reduce focal length?
Yes, speed boosters reduce focal length by a factor of 0.71x for most M43 adapters. A 50mm full frame lens becomes a 53mm equivalent on M43 with a 0.71x reducer (50 x 0.71 x 1.5 crop factor). The 0.64x speed boosters reduce focal length by 0.64x but typically require APS-C lenses to avoid vignetting. The reduction in focal length also concentrates the light onto the smaller sensor, which effectively gives you about 1 stop more aperture.
Are speed boosters worth buying for M43?
Speed boosters are worth buying for M43 if you already own Canon EF, Nikon F, or other full frame glass, or if you want the shallow depth of field and low-light performance of fast full frame lenses. The 0.71x focal reduction plus 1 stop of light gain makes adapted f/1.4 lenses behave like f/1.0 on M43, which is a meaningful difference. For users who primarily shoot native M43 glass, a speed booster is less essential. For video shooters using the Sigma 18-35mm f/1.8, a speed booster is essentially required to get the wide-aperture zoom range that the lens is famous for.
Final Recommendations
After testing all 12 of the best speed boosters for Micro Four Thirds cameras, my top picks depend on what you already own. For Canon EF shooters, the VILTROX EF-M2 PRO is the best balance of autofocus reliability, security locking, and value. For Nikon F shooters on a budget, the VILTROX NF-M43X delivers Metabones-quality optics at a fraction of the price. For Blackmagic BMPCC 4K users who need the absolute best image quality, the Metabones T Speed Booster ULTRA is the right pick despite the premium price.
For photographers who own classic Four Thirds Zuiko glass, the Hersmay or FocusFoto adapters are the most affordable way to mount those legendary lenses on modern M43 bodies. The Olympus MMF-3 used market is also worth exploring for OEM-quality alternatives.
Whatever you choose, a speed booster is one of the most impactful accessories you can buy for a Micro Four Thirds camera. The 0.71x focal reduction plus 1 stop of light gain transforms adapted full frame lenses into versatile tools that are otherwise impossible to achieve natively on M43. In 2026, the lineup is more mature than ever, and there is an adapter for every mount and budget.