Review: Metabones Speed Booster XL Adapter

More Boost for Your Money
By Sol March in Resources

Is Metabones’ Speed Booster XL the adapter to get for 4K shooters?

Soon after the Panasonic GH4 was released, there were rumblings of a Speed Booster specifically designed to maximize performance when shooting 4K with this camera.

It took a little over a year, but the Speed Booster XL is finally here.

The XL is the same price as the standard Speed Booster, but it features a modified optical design that delivers a wider field of view (FOV) than the original adapter. This is a welcome feature for many shooters, but the XL also comes with a few caveats that present some issues in certain situations.

B&H sent the Speed Booster XL for Nikon lenses over and I’ve been shooting with it exclusively for the past month. Read on to find out where it excels and where it falls short.

Just the Stats Ma’am

  • Adapter type: Passive (no electronics)
  • Lens mount: Nikon F-mount / Nikon G-mount
  • Camera mount: Micro Four Thirds (Panasonic GH4, Blackmagic Pocket, etc.)
  • Focal Reduction: 0.64x
  • Aperture Control: Yes (manual ring)
  • Autofocus: No
  • Weight: 173g
  • Warranty: 1 year
  • Price: $479 (check current price)

Speed Booster Magic: Increased FOV & Brightness

Metabones’ Speed Booster is a special kind of adapter called a “focal reducer”. Focal reducers are unique in that they contain optics that provide two primary benefits– a wider field of view and a brighter image.

Wider Field of View

As the name implies, a focal reducer reduces the focal length of a lens, which results in a wider field of view (FOV). The Speed Booster XL has a 0.64x focal reduction factor, which is used to calculate a lens’ new focal length when used with the adapter.

For example, a 50mm lens has a 32mm focal length when used with the Speed Booster XL.


Metabones’ standard Speed Booster has a 0.71x focal reduction, but the XL takes things even further to compensate for the Panasonic GH4’s 4K recording modes, which use a smaller portion of the sensor than when shooting in HD.


As a result of the increased focal reduction, the Speed Booster XL provides a Super 35 FOV when shooting in 4K on the GH4.

You get an even wider FOV when shooting in HD, since the GH4 uses more of its sensor in that mode. However, the XL’s increased focal reduction can also introduce issues with certain lenses– such as vignetting– when shooting stills or HD video (more details on this later in the review).

Boosted Brightness

A lens’ aperture is also affected as the Speed Booster’s optics concentrate light to give you a brighter image.

The XL’s 0.64x focal reduction effectively increases a lens’ brightness by 1-1/3 stops. Since a 1 stop increase doubles the brightness of an image, the difference in brightness between a standard adapter (without optics) and the Speed Booster XL is dramatic.

Darker image with standard adapterBrighter image with Speed Booster

This boost in brightness is very helpful when shooting in low-light situations, but it’s even helpful in marginally dim environments as it allows you to get a proper exposure with a lower ISO, resulting in a cleaner image with less noise.

Passive Adapter

Metabones makes a Speed Booster XL for various lens mounts such as Canon EF and Nikon F/G.

While the Canon EF adapter is an active adapter with electronics that allow in-camera aperture control and autofocus, the Nikon-mount Speed Booster is passive. In fact, all Nikon-mount adapters are passive.

Passive adapter

Passive adapters provide no electronic connection between the camera and the lens, so all controls are fully manual. This means no in-camera aperture control and no autofocus, which could be a benefit or an issue depending on your needs.

For example, if you use vintage lenses or cine lenses, everything is manually controlled anyway, so a passive adapter wouldn’t hinder you. However, if you shoot with modern Nikon G-mount lenses, then the lack of autofocus when shooting stills may take some getting used to.

Aperture Control

Thankfully, a passive adapter does not mean you have no control over aperture. Instead of in-camera aperture control using the camera’s dials, you can adjust a lens’ aperture using the manual ring built into the XL adapter itself.

Speed Booster XL has a manual aperture ring

The XL’s manual aperture ring is particularly useful when using modern Nikon G-mount lenses that do not have a manual aperture ring of their own.

Sigma 18-35mm f/1.8

However, the XL’s clickless aperture ring may be worth using with Nikon F-mount lenses as well since it allows for smooth aperture adjustments. This is useful when you need to smoothly change exposure while rolling, such as when moving from interior to exterior environments mid-shot.

The XL’s aperture ring also has a longer throw that most (if not all) other adapters out there. Most adapters have an aperture ring with a very short amount of travel from fully opening the lens’ aperture to fully closing it, but the Speed Booster XL’s aperture ring has about 45° of rotation. This gives you a good amount of control when making small adjustments to the lens’ aperture.

Speed Booster XL aperture ring has about 45 degress of throw

Perhaps the only downside of the XL’s manual aperture ring is that it is not easy to set the lens to a very specific aperture. The markings on the aperture ring represent 1 stop increments, but it’s not universally accurate for all lenses. As a result, while an setting a lens’ aperture to f/2.5 is dead simple with a native lens, it’s a bit of a shot in the dark with the XL’s aperture ring.

Numbered markings on Speed Booster XL aperture ring

Image Quality

Putting extra glass between the lens and your camera usually isn’t a recipe for maintaining high image quality, but Metabones nailed it with the optical design used in their Speed Boosters.

Speed Booster XL has high quality optics

Image quality is not lowered when using the Speed Booster, even when shooting stills. In fact, though it may be hard to detect, Metabones say that the Speed Booster’s optical design actually improves a lens’ performance.

This is the biggest difference between Metabones’ Speed Booster and cheaper focal reducers from other manufacturers, which noticeably reduce image quality. If you need the best image quality for video and stills, Metabones’ Speed Boosters are worth the higher price.

Many lenses have increased softness or chromatic aberration at their edges, so you may notice more of this with the Speed Booster XL since its higher focal reduction makes more of a lens’ edges visible. Due to the higher crop factor, the edges aren’t visible when shooting in 4K on the GH4, but it may be more noticeable when shooting stills, as the entire sensor is used.


Vignetting can also be an issue when using the Speed Booster XL depending on what lenses you use.

Here’s the breakdown:

  • Full frame lenses — No vignetting in any recording mode.
  • APS-C lenses — No vignetting when shooting in 4K, but vignetting may occur in other recording modes (stills, HD, etc.).

APS-C lenses may exhibit vignetting in some recording modes because they only need to project an image circle that will cover an APS-C sensor. When using the GH4’s full sensor to shoot stills or HD video, the XL’s 0.64x focal reduction actually requires a larger image circle than an APS-C lens may provide.

APS-C lenses may vignette with the Speed Booster XL in some reco

By contrast, full frame lenses project an image circle that covers a full frame 35mm sensor, and thus also provide an image circle large enough for the XL in any mode.

Full frame lenses provide full coverage for the Speed Booster XL

Here are some examples of the vignetting you can get when using an APS-C lens with the Speed Booster XL in various recording modes. These tests were shot with Sigma’s 18-35mm f/1.8 zoom lens at 18mm.

Panasonic GH4 recording in 4K (UHD)

Speed Booster XL FOV in 4K (UHD)

Panasonic GH4 recording in HD

Speed Booster XL FOV in HD

Panasonic GH4 4:3 Still

Still Photo Vignetting with Speed Booster XL

As you can see, while there was no vignetting in 4K or HD, vignetting was quite heavy when shooting stills with the Speed Booster XL using an APS-C lens. Depending on the lens, vignetting may also occur when shooting in HD.

Build Quality

Metabones is known for making solid adapters and the Speed Booster XL is no exception. The adapter is solid and feels like it is built to last.

Solid build quality

That said, while I have yet to experience any issues with Metabones’ adapters, it’s worth noting that others have reported issues where their Metabones adapters had loose screws or fittings. In many cases these issues have been resolved by getting a replacement part from Metabones, but the company has a reputation of being slow to respond.

As such, it may be a good idea to purchase your adapter from a local distributor that has a good return policy in case you get a defective unit and need to exchange it.


The Speed Booster XL has a small amount of play (1mm) between the adapter and the camera, but this almost always the case when using lenses and adapters designed for still photography cameras (even native lenses).

About 1mm of play between the Speed Booster XL and the GH4's len

There is also a tiny bit of play between the lens and the adapter, but overall it is a solid fit.

Is the Speed Booster XL Right for You?

The Speed Booster XL is a well-built adapter that delivers solid image quality and a wider FOV than the standard Speed Booster.

The XL’s increased field of view is noticeable, but not extremely different compared to the standard Speed Booster– it’s basically the equivalent of shooting with a 25mm lens instead of a 28mm lens. Therefore, if you already have a Speed Booster, you’re not really missing much.

You also give up some flexibility when using the XL compared to a standard Speed Booster, both in terms of lens options and recording modes due to the increased chance of vignetting when using APS-C lenses.

If you only shoot in 4K or only use full-frame lenses, you can benefit from the XL’s slightly wider FOV and increased brightness.

Remember: Even if you shoot primarily in 4K, you still need to drop down to HD to shoot slow motion footage with the GH4.

On the other hand, you may have to take a few steps back to get the same field of view with a standard Speed Booster, but vignetting won’t be something you have to worry about in any recording mode, giving you more flexibility in selecting lenses to shoot with.

It’s a great adapter, but if you use APS-C lenses (especially wide-angle lenses), you may want to take your lenses to the camera store to test them for vignetting before taking the plunge on the Speed Booster XL.


Lens Options for the Panasonic GH4


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