Speed Booster Ultra Review: Metabones Reference vs Viltrox Budget

A focal reducer is one of the strangest and most useful accessories in video. Put one between a full-frame lens and a smaller sensor and the lens gets wider and brighter at the same time, which can turn a bag of old glass into a new kit.

The catch is that adapters live or die on their electronics. Autofocus, aperture control and lens communication either work smoothly or fail at the worst moment, and the gap between the reference brand and the budget one shows up exactly there.

Below is what a speed booster changes, the budget alternative side by side, where adapters fail, and which body pairs with which adapter.

The Metabones Speed Booster Ultra remains the definitive reference point for glass adapters, while the Viltrox EF-M2II offers a budget alternative that gets close even though the connections aren't quite at that premium level.

You won't be paying Metabones prices when you choose the Viltrox, which still brings life to old lenses across various camera systems. One S5II owner has found the autofocus smooth when it works, which sums up the budget-adapter story: it's great when it works.

What the Speed Booster Changes

This 0.71x reduction creates a wider field of view while making your lenses much faster, which helps you capture more light when you're shooting in very dim spots. One owner has said it gives life to old lenses, so they don't have to sell them, and the mechanism comes down to one number: same glass, wider and faster.

One landscape photographer loves their new Nikon Z7 II and 40-120mm lens but missed their old F-mount lenses, and an adapter brought them back. The Viltrox is the budget build, and the Metabones is the one many users want. It's easy to bridge the gap between old gear and the cameras you use right now.

On a budget, the Viltrox might do the job, but the Metabones is the choice for the best possible results from vintage glass.

The primes stay. The focal reduction is the physics: 0.71x on the focal length, one stop on the aperture, and the full-frame look on a smaller sensor. One Viltrox owner had returned another brand because it wouldn't focus, and this one focuses without problems.

The Viltrox Side by Side

The Viltrox EF-M2II rates 4.1 across 250 ratings, a much deeper sample than the Metabones has.

To use old EF lenses on a Sony a7II, this budget Viltrox adapter works without major issues or annoying glitches during a shoot. One owner bought it after a cheaper version occasionally gave them trouble in tight situations. It isn't quite as good as the Metabones, but you aren't paying that high cost for the build.

While the Viltrox gives life to old lenses on the Nikon Z7II and ZFC, it seems to struggle when using the Blackmagic Pyxis L-mount camera.

Another buyer has found that it works well on the Nikon Z50II, for both photo and video AF modes. One 1-star Pyxis owner tried hard to make it work as an L-to-EF adapter for their Canon lenses, and the lesson is that the EF-M2II is an EF-to-M43 adapter, not an L-mount one. Check the mount twice.

Where Adapters Fail

One buyer has felt disappointed because the Metabones speed booster arrived in a box that looked already used, which is a big letdown when you spend your money on brand new gear. One owner of six months has had to research which lenses fit and work with the adapter.

The research is the tax. The compatibility list is where the answer lives. The owner who returned another brand already showed the pattern, and it repeats across brands.

A user has found the autofocus not good, and has said the connections aren't at Metabones level, but you aren't paying Metabones prices either

Which Body Pairs with Which Adapter

The Metabones T Speed Booster is built for the BMPCC4K's T-mount, and that specificity is its strength: one body, one job, engineered for it.

The 0.71x reduction turns the EF glass into a wider, faster version of itself on the Blackmagic sensor. The Metabones has only 30 ratings, though, and just one written review, so its 4.8 average rests on a thin sample.

The pairing rule is mount-first: T-mount for the BMPCC4K, the EF-M2II for Micro Four Thirds, and the Sony E and Nikon Z bodies have their own Viltrox variants.

Owners have confirmed it across mounts: one now uses EF lenses on a Sony a7II without any issues, another has found it focuses and works fine on a Nikon Zfc, and one more has found AF works perfectly for video and photos on the Nikon Z50II, the newest body in the set.

That Z50II owner pointed out that there are almost no reviews for that camera, and the Zfc owner had no official Nikon adapter to compare against, so treat both as single reports.

Frequently Asked Questions

For the M43, Sony E, and Nikon Z bodies, the Viltrox EF-M2II is the budget adapter, with owners confirming it on a Sony a7II and a Nikon Zfc. The Viltrox M50 page covers the EF-M side. This adapter helps save your F-mount lenses on newer Nikon bodies, and gives life to older mirrorless gear.

Is Metabones Worth It over Viltrox?

That 4-star reviewer's whole answer is that the connections aren't at Metabones level, but neither is the price, so the question is whether your shooting punishes the difference. One Viltrox owner can't imagine how the Metabones could be better and has called it the best value for the price.

Does the Autofocus Work?

The S5II owner has found the autofocus smooth when it works, and the reviewer has found it not good, which is the honest spread. For stills on slower subjects it holds. For run-and-gun video, plan on manual focus or the native-lens fallback.

Which Mount Do I Need?

Mount-first: the BMPCC4K takes the T-mount Metabones, Micro Four Thirds bodies take the EF-M2II, and Sony E and Nikon Z have their own variants. The research step isn't optional, as the six-month owner has found, and it applies per body.

Can I Use Any EF Lens?

No. One owner who bought it about half a year ago has had to research which lenses fit and work with the adapter. Third-party EF glass, EF-S, and speed-booster-stacked setups each have caveats, and the compatibility list is per-body.

What About the Used-Box Risk?

The Metabones has a 4.8 average, but one buyer still received an opened box that looked used. Buy from the listing that ships sealed, and check the serial against the warranty registration before the return window closes.

The everyday-tier comparison applies to the price question: know which tier of failure you can live with before the order.

Check B&H's adapter stock for the Metabones tiers, and PetaPixel's adapter coverage reads the mount-adapter market from the photo side, and No Film School's lens guides explain the focal-reducer math for the film side. The adapter field guide is this page's sibling, and the R50's page is the no-adapter alternative body.