A speed booster is a lens mount adapter with extra optical glass inside. It fits a lens designed for a bigger sensor onto a smaller-sensor mirrorless body, reducing the crop factor a little. The usual figure is 0.71x, so a lens behaves as a slightly wider one, and makers say it also lets in about one stop more light.
The six adapters below all take Canon EF lenses and cover Sony E, Fujifilm X, Canon EF-M, Nikon Z and Micro Four Thirds bodies. Details come from each product’s listing page. We have not used these adapters ourselves. Autofocus and optical statements are the makers’ own, and several listings contradict themselves, which we note.
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What to Look For
| Feature | Why it matters |
|---|---|
| Camera mount | The adapter must match your body, such as Sony E, Fuji X or Nikon Z |
| Reduction ratio | 0.71x widens the view of the lens |
| Autofocus support | Some adapters pass autofocus and aperture control; others are manual |
| Image circle | Boosters can be designed for smaller sensors and may vignette on full frame |
| Firmware port | A USB port lets the maker update compatibility |
Specs at a Glance
| Adapter | Camera mount | Focus | Notes |
|---|---|---|---|
| Viltrox EF-E II | Sony E | Autofocus (CDAF and PDAF) | 268 g; USB upgrade |
| Viltrox EF-FX2 Pro | Fujifilm X | Autofocus | 162.5 g; micro USB |
| Viltrox EF-EOS M2 | Canon EF-M | Autofocus | 145 g; 1/4 inch tripod socket |
| Metabones T Speed Booster ULTRA | Canon EF-M | Conflicting listing | 10.4 oz; tripod foot |
| Viltrox EF-Z2 | Nikon Z | Autofocus | 268 g; zinc alloy; USB upgrade |
| Viltrox EF-M2 Pro | Micro Four Thirds | Autofocus | Rotating lock; USB-C upgrade |
The 6 Best Speed Boosters for Mirrorless Cameras
1. Viltrox EF-E II (Canon EF to Sony E)
A 0.71x booster of CNC aluminum weighing 268 grams, with four glass groups, gold-plated contacts, autofocus using CDAF and PDAF and a USB port for updates. The maker says it covers an APS-C image circle, so on a full-frame Sony body the camera needs its APS-C or Super 35 mode set to Auto or On. The bullets mention an aperture gain of 3 stops, which does not match the usual one-stop figure on other listings, so treat it with caution.
Suits: Sony E-mount APS-C bodies. Strengths: autofocus and firmware updates. Weaknesses: an unclear stop gain. Skip it if you shoot full frame without a crop mode.
2. Viltrox EF-FX2 Pro (Canon EF to Fuji X)
A 162.5 gram all-metal adapter that passes autofocus, aperture control and EXIF data to Fujifilm X-mount bodies, with a micro USB port for updates. The maker explains that the focal length is multiplied by 0.71 and then by the 1.5 crop factor. The spec table describes it as waterproof, but the bullets do not, so we make no weather claim.
Suits: Fujifilm APS-C bodies. Strengths: a light all-metal body at 162.5 grams. Weaknesses: contradictory weather wording. Skip it if you use another mount.
3. Viltrox EF-EOS M2 (Canon EF to EF-M)
A 145 gram all-metal adapter with chrome-plated brass mounts, a 0.71x reduction, a stated one-stop aperture gain, autofocus and aperture control from the EOS M body, and a 1/4 inch tripod socket on the bottom. It lists the EOS M, M2, M3, M5, M6, M10, M50 and M100 series among compatible bodies.
Suits: Canon EOS M bodies. Strengths: the lightest listed weight and a tripod socket. Weaknesses: it fits EF-M bodies only. Skip it if you are not using an EF-M body.
4. Metabones T Speed Booster ULTRA 0.71x (EF to EF-M)
A heavier 10.4 ounce adapter with 5 elements in 4 groups, a 0.71x ratio, an f/0.9 maximum output the maker highlights, a built-in tripod foot, a 1/4 inch tripod thread and front and rear caps. The spec table lists manual focus and a teleconverter type, yet the item highlight mentions autofocus, so confirm the focus behavior with the seller.
Suits: heavier EF lenses on an EOS M body. Strengths: a tripod foot and multi-element optics. Weaknesses: conflicting focus information. Skip it if you need confirmed autofocus.
View Metabones T Speed Booster ULTRA 0.71x Adapter for Canon EF to -M Camera on Amazon
5. Viltrox EF-Z2 (Canon EF to Nikon Z)
A 268 gram (13.44 ounce) zinc alloy adapter with a brass-plated bayonet, 0.71x reduction, autofocus through copper contacts, a USB port for firmware updates and 1/4 inch tripod holes. The listing names the Z5, Z50, Z6, Z6II, Z7, Z7II, Z8, Z9 and Zfc as compatible.
Suits: Nikon Z bodies, including the APS-C Z50 and Zfc. Strengths: a broad body list and a firmware port. Weaknesses: the heaviest in the group. Skip it if you want a light adapter.
6. Viltrox EF-M2 Pro (Canon EF to Micro Four Thirds)
A Micro Four Thirds adapter with a 0.71x reduction, autofocus, aperture control, a rotating lock buckle and a USB-C firmware port. The bullets give 181 grams while the table shows 0.3 kg, and the table says no image stabilization while the bullets mention an IS function, so these details are unclear. Micro Four Thirds sensors are smaller than APS-C.
Suits: Panasonic and OM System bodies. Strengths: a lock buckle and a long body list. Weaknesses: conflicting weight and stabilization details. Skip it if you shoot APS-C.
Best Picks by Category
These labels come from the price, star rating and number of ratings shown on each Amazon listing on November 2, 2026. They summarize listing data and are not hands-on test results.
- Top rated: Metabones T Speed Booster ULTRA 0.71x (EF to EF-M) — 5 out of 5 from 5 ratings, about $499.
- Most reviewed: Viltrox EF-FX2 Pro (Canon EF to Fuji X) — 1,476 ratings averaging 4 out of 5.
- Best value: Viltrox EF-Z2 (Canon EF to Nikon Z) — the lowest-priced pick with a 4.5 rating and at least 200 ratings, about $218.
- Lowest price: Viltrox EF-EOS M2 (Canon EF to EF-M) — about $156, rated 4 out of 5.
- Premium option: Metabones T Speed Booster ULTRA 0.71x (EF to EF-M) — about $499, rated 5 out of 5.
Price, Rating and Review Comparison
The table sorts the picks by price and adds the star rating and the number of ratings, which shows how much feedback sits behind each average. Prices change often, so confirm the current price on Amazon.
| Product | Price | Rating | Ratings | Price tier |
|---|---|---|---|---|
| Viltrox EF-EOS M2 (Canon EF to EF-M) | $156 | 4 / 5 | 1,476 | Mid-range |
| Viltrox EF-E II (Canon EF to Sony E) | $188 | 4 / 5 | 83 | Mid-range |
| Viltrox EF-FX2 Pro (Canon EF to Fuji X) | $198 | 4 / 5 | 1,476 | Mid-range |
| Viltrox EF-Z2 (Canon EF to Nikon Z) | $218 | 4.5 / 5 | 698 | Mid-range |
| Viltrox EF-M2 Pro (Canon EF to Micro Four Thirds) | $218 | 4 / 5 | 1,476 | Mid-range |
| Metabones T Speed Booster ULTRA 0.71x (EF to EF-M) | $499 | 5 / 5 | 5 | Premium |
How Much Feedback Backs Each Rating
A high average from a handful of ratings is weaker evidence than a slightly lower average from thousands. Here is how the sample size looks for each pick.
- Viltrox EF-E II (Canon EF to Sony E): only 83 ratings, so treat the 4 average cautiously.
- Viltrox EF-FX2 Pro (Canon EF to Fuji X): 1,476 ratings, a large sample behind its 4 average.
- Viltrox EF-EOS M2 (Canon EF to EF-M): 1,476 ratings, a large sample behind its 4 average.
- Metabones T Speed Booster ULTRA 0.71x (EF to EF-M): only 5 ratings, so treat the 5 average cautiously.
- Viltrox EF-Z2 (Canon EF to Nikon Z): 698 ratings, a moderate sample behind its 4.5 average.
- Viltrox EF-M2 Pro (Canon EF to Micro Four Thirds): 1,476 ratings, a large sample behind its 4 average.
Care and Setup
- Update the adapter firmware through its USB port if the maker offers it.
- Keep both mounts capped when the adapter is not in use.
- Support heavy lenses by the lens barrel or a tripod foot, not the adapter.
- Wipe the electronic contacts with a dry cloth only.
Mistakes to Avoid
- Buying for the wrong camera mount.
- Expecting autofocus from every lens.
- Using an APS-C booster on full frame without a crop mode.
- Trusting one listing line when the details conflict.
Speed Booster FAQ
Does a speed booster add light?
Makers say it gains about one stop, although one listing here claims three. Check the maker’s own notes.
Can I use EF-S lenses?
One listing mentions EF and EF-S lenses; check each listing for the lens types it names.
The Short Version
For Sony E, the Viltrox EF-E II. For Fuji X, the EF-FX2 Pro. For a light Canon EF-M option, the EF-EOS M2. For a tripod foot, the Metabones. For Nikon Z, the EF-Z2. For Micro Four Thirds, the EF-M2 Pro.
