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If you’ve been in the world of filmmaking and videography for some time, you’ve probably heard of speed boosters.
These devices, properly known as focal reducers, are often very expensive and little understood. And considering how expensive focal reducers can be, it may not seem worth it to make the investment.
Yet, if you’re looking to get an extra stop of light from your lenses, adapt non-native lenses, and/or make your lenses capture a wider angle, focal reducers are for you.
The most recognizable brand is the Metabones Speed Booster, and they are the reason focal reducers are often referred to as speed boosters.
for EF to M43 mount on Amazon.
Metabones Speed Boosters are top of the line adapters and their prices reflect that. And the high prices make this technology seem inaccessible to a lot of filmmakers.
But, luckily, there are plenty of cheap and lesser-known alternatives on the market, and we’ll take a look at some of the best out there in this guide.
But first, we’ll offer a brief overview of how the focal reducers function. If you’ve never used a focal reducer, we recommend you read this guide first and get to know how focal reducers work on a basic level.
If you have used focal reducers though, or are familiar with their functionality, you can skip the next section of the article and jump straight to the best alternatives to the Metabones Speedbooster.
What is a Focal Reducer?
A focal reducer is a lens adapter that adapts larger lenses to smaller sized a.k.a. crop sized sensors. For example, you can use a full-frame Canon lens with EF-Mount on a Micro-Four-Thirds camera.
Now, you can get a lot of adapters – electronic adapters as well as “dummy” adapter – which does that as well.
But a focal reducer is constructed in such a way, that you do not only gain an extra stop of light but also a wider field of view when you do so.
Focal reducers only exist for mirrorless cameras, because the mirror in a DSLR camera would get in a way, because of the way these adapters are functioning.
Focal reducers exist for a lot of different mirrorless cameras with cropped sensors. The different sensor-sizes will affect the impact focal reducers have.
In this guide, we will be focusing specifically on Micro Four Thirds (MFT) mounts. When you put a focal reducer on an MFT sensor, you’ll actually get a wider field-of-view than you get on a super 35mm/APS-C sensor.
How Does A Focal Reducer (Speedbooster) Work?
A large factor that makes focal reducers different from standard lens adapters, and more expensive, is that they have glass in them.
The addition of glass in these adapters effectively puts a lens between the original lens and the camera, which shortens the focal length.
Instead of measuring the distance from your lens to the sensor, the focal length of your camera is now affected by a piece of glass between the lens and the sensor.
And since the f-number is found by taking the focal length and dividing it by the aperture diameter, reducing the focal length makes the f-number smaller and therefore faster.
Gain One Stop of Extra Light
Also, the added glass is the reason focal reducers make the lens “faster,” adding up to an extra stop of exposure. The curved glass of the focal reducer concentrates the light entering through your lens onto the sensor.
So while the same amount of light passes through the lenses, it’s essentially packed into a smaller area of the sensor.
This can be very helpful if you need to shoot in low light or achieve a very shallow depth of field.
What this also means is that for a focal reducer to work, the lens should be designed for a larger sensor than that of the camera.
For example, you can use a lens designed for a full-frame or APC-S sensor on an MFT camera. But you can’t do it the other way around without heavy vignetting.
Something to take into account is that while focal reducers boost the maximum aperture of the lens, they also boost the minimum.
If you want to set your camera to something like f/22, you will need to remove your booster.
Metabones vs Cheaper Alternatives
Now, with focal reducers, you get what you pay for. That doesn’t mean that you can’t use more budget-friendly alternatives. In fact, a lot of people do so with great success, amateurs as well as professionals.
However, there are some caveats you should be aware of.
A benefit of using a high-quality focal reducer like Metabones is that the Modulation Transfer Function (MTF – not to be confused with MFT) of the lens is also increased.
What this means is that the resolution and the contrast of the lens are improved upon. Lenses tend to get softer and have less contrast as you move from the center to the edges.
But with a good focal reducer like the ones from Metabones, your lens actually becomes sharper and has more contrast near the edges.
This is a point where the cheaper alternatives often fall short. Instead of increasing the MTF they actually decrease it, which results in a softer image. But a softer image isn’t always a bad thing when it comes to video.
No Electronic Connections
Many cheap focal reducers also do not offer an electronic connection between the lens and your camera.
If you’re using a cine lens or manually controlled lens, this won’t cause any issues, but if your lens can only have the aperture and focus adjusted in-camera, then it is strongly suggested to spend the extra money and acquire an adapter that has an electronic connection.
The issues of electronic connection will be covered in more detail as we cover the specifications of our recommended focal reducers.
Notes on Adapting Micro Four Thirds Lenses
Adapting lenses to MFT lenses using a focal reducer is helpful due to the small size of the MFT sensor.
The small size of an MFT-sensor doesn’t make it as good in low-light as APS-C or full-frame sensors. So having the ability to gain an extra stop of light is great.
Furthermore, on MFT, it can be difficult to find truly wide-angle lenses, and you’re limited to a few options. One of these is the amazing Laowa 7.5mm f/2.0, which you can read our review of here.
Focal reducers can be very helpful if you’re like me and like the look of wide-angle lenses but shoot with anything besides a full-frame sensor.
These adapters give those of us who shoot on crop sensors a much wider array of glass to choose from.
A Quick Note that there are special Special Focal Reducers for BMPCC 4K
to BMPCC4K T Speed Booster
Ultra 0.71x, on Amazon.
Due to the filter stack thickness of 2.4mm found in the Blackmagic Cinema Camera 4K (compared to the 4mm found in standard Micro-Four-Thirds cameras), Metabones has developed a special series of focal reducers for this camera.
The special version differs from the ordinary Metabones XL and Ultra in that 1) it offers a new optical design optimized for the BMPCC4K, which gives you a sharper image across the lens, and 2) it comes with a longer tripod mount that matches the height of the BMPCC 4K camera body.
While you can use the ordinary Metabones Ultra and XL on BMPCC4K, you can’t use the special BMPCC4K edition on other MFT systems.
So if you own a BMPCC4K you need to be aware of this. You can find Metabones Speed Boosters for BMPCC4K here on Adorama – both cine and standard versions.
How to Calculate the New Focal Length
I often see a lot of bad math when people discuss how to calculate the new focal length when using a focal reducer. But it’s actually pretty simple.
The equation looks like this:
Focal Length x Crop Factor x Focal Reduction
Or in terms of hardware:
Focal lenght (lens in mm) x Crop Factor (camera sensor type) x Focal Reduction (type of focal reducer)
Let’s look at an example:
The Panasonic GH5 is an MFT system, which means you get a 2x crop factor.
We now take a Canon EF 100mm lens and put it on the GH5 with a dummy adapter (non-focal reducer).
The field-of-view we now get from this lens on the GH5 corresponds to the field-of-view of a 200mm lens on a Canon full-frame camera because of the 2x crop factor: 2 x 100mm = 200mm.
Now we put a Metabones Speedbooster XL, which offers 0.64x focal reduction, between the GH5 and the lens.
The new focal length is 200mm x 0.64 = 128mm. In other words, the 100mm lens now gives you the equivalent field-of-view of a 128mm lens on a full-frame system.
If we were to use the Metabones Speedbooster Ultra instead, which has a 0.71x focal reduction, we would get the field-of-view of using a 142mm lens on a full-frame camera (200mm x 0.71 = 142mm).
Lots of Lenses to Choose From
With a focal reducer, you suddenly have the option to adopt a crazy amount of lenses from both APS-C and full-frame camera systems.
You can even adopt vintage glass. For example, Metabones makes a focal reducer for Canon FD-mount glass to MFT.
Speed Booster on Amazon.
If you own cine lenses, Metabones also makes special adapters for cine glass.
And this is where the MFT-system really shines: you can use so many different lenses from all kinds of systems with all kinds of adapters – focal reducers being only one of them.
Using focal reducers can affect image quality, though certain models and brands do a good job of limiting the impacts. As with any adapter and cheap lenses, there are risks of field curvature, distortion, light leaks, and chromatic aberration.
Ensuring that you get the best focal reducer for your price point is extremely important to save yourself from any headaches in the future.
Cheap Alternatives To The Metabones Speedbooster (For MFT Mounts)
While Metabones certainly sets the standard in terms of focal reducers, luckily for us independent filmmakers, other companies are putting their hats in the ring.
Below I have compiled a list of the best alternatives to the Metabones Speedbooster for MFT cameras. Many of these manufacturers also make adapters to other mounts such as APS-C.
The first four have no electronic connection, so cine lenses or manual lenses, where you can set the aperture on the lens, are required.
1. Pixco Lens Adapter Speed Booster For Canon EF Lens To Micro M4/3
Weight: 8.8 oz / 0.25 kg
Magnification: 0.7x
Lens Mount: Canon EF
Camera Mount: Micro Four Thirds
Strengths: The Pixco Speed Booster adapts full-frame lenses Canon lenses for Micro Four Thirds. This can be super helpful for cine lenses such as Rokinon lenses with an EF mount.
There is no electronic connection, so this adapter is only usable with lenses that have fully manual focus and aperture adjustment. This adapter is a very affordable price and also increases exposure by one stop with a 0.7x magnification.
Weaknesses: Having no electronic connection limits the usability of this adapter to cine lenses. Also, as expected at its price point, the image will be soft with some vignettes.
If you’re adapting expensive glass, this isn’t the adapter for you. The build quality isn’t impressive, and it can be difficult to fit the lenses. When an adapter like this is very stiff, be sure to attach the lenses when the lens isn’t joined with the camera.
Description: For the price, the Pixco Speed Booster is a great option. While there are issues with the build quality, blurry images, and vignettes, it is drastically cheaper than many of the alternatives and can be a great introduction to focal reducers. If you are looking to adopt some budget cine lenses, this is a solid choice without breaking the bank.
Check the current price on Amazon.
2. Mitakon Zhongyi Canon EF To Micro Four Thirds Turbo Adapter Mark II
Weight: 8.0 oz / 0.23 kg
Magnification: 0.726x
Lens Mount: Canon EF
Camera Mount: Micro Four Thirds
Strengths: The Mitakon Zhongyi is a solid and well-built adapter. This adapter will add an extra 0.7 stop to your lens and has a 0.726x magnification which is great for an MFT sensor. Like the Pixco adapter, there is no electronic connection, so it requires manually adjustable focus and aperture.
Weaknesses: When compared to expensive models this adapter has poor image quality and won’t produce the sharpest image. There are also some issues with a vignette and no electronic connection. Since there is no electronic communication between the camera and lens, cine lenses and manual lenses are required to use this booster.
Description: This is another solid focal reducer for the money. For such a cheap price, there is no electronic connection between the camera and the lens which can cause issues if you use lenses that require such connection (certain Canon Lenses need electronics to change focus).
However, if you’re using prime lenses or cine lenses, you should be fine. The build of this focal reducer is durable and there are only minor concessions in image quality that include vignettes and some blurring. For the price, this can be a great booster to combat the MFT crop factor, add 0.7 stops of exposure, and increase the angle of your lenses.
Check the current price on Adorama (more options available).
Check the current price on Amazon.
3. Fotodiox Pro Excell+1 Lens Adapter OM Lens To MFT Camera
Weight: 4.8 oz / 0.14kg
Magnification: 0.72x
Lens Mount: OM
Camera Mount: Micro Four Thirds
Strengths: The strengths of this Fotodiox adapter are similar to the aforementioned lenses, offering a .72x crop factor and an extra stop in aperture. The Fotodiox Pro Excel line also offers many different lens mounts to adapt to MFT cameras, giving a nice array of options if you have a variety of lenses you’re looking to adapt.
Weaknesses: There is no electronic communication between the camera and this lens, so focus and aperture will need to be adjusted manually. Additionally, there are image quality issues with this lens, with the image becoming especially soft when the aperture is set below f/4.
Description: The strengths of Fotodiox are the large array of options they have when looking at lens adapters with optics. This can allow you to have a sense of consistency between lenses.
However, the issues that persist with open apertures limit the usefulness of this adapter. Even at a medium f-stop, the image will not be sharp. Furthermore, as the price point rises it may be much more appealing to acquire a booster with electronic connection unless you plan on only using manual lenses.
Check the current price on Amazon (more options available).
Check the current price on Amazon.
4. Kipon Baveyes 0.7x Focal Reducer For Canon EF To Micro Four Thirds
Weight: 9.6 oz / 0.27 kg
Magnification: 0.71x
Lens Mount: Canon EF
Camera Mount: Micro Four Thirds
Strengths: The Kipon Baveyes gives you everything you’d expect from a focal reducer without electronic adaptation. It does not noticeably affect the image quality while giving an extra stop in aperture and 0.71x magnification.
Weaknesses: The only major weakness with this focal reducer is the lack of electronics. You cannot change the aperture on digital lenses which can be an issue. While this focal reducer has a very solid build, the fit can be tight at so be careful when attaching lenses.
Description: The Kipon Baveyes focal reducer is a great option if you can find it, though it does lack an electronic connection. It produces a great quality image with no noticeable drop in quality. The mount can be a bit tight, so be sure to be careful mounting your lenses, but it is otherwise a solid focal reducer.
Check the current price on Adorama (more options available).
Check the current price on Amazon.
5. Viltrox EF-M2 Lens Adapter For Canon EF Lens To Micro Four Thirds
Weight: 4.90 oz / 0.14 kg
Magnification: 0.71x
Lens Mount: Canon EF
Camera Mount: Micro Four Thirds
Strengths: The Viltrox EF-M2 Adapter connects the electronics of the lens to the camera, so autofocus and aperture can work from the camera. This will drastically increase the options of lenses you can use. Additionally, it has the same benefits as other boosters, giving an extra .6 stops and 0.71x magnification. The image quality is solid, though minor concessions will be made.
Weaknesses: While there is an electronic connection, you can’t switch to manual while the camera is on. Often times this won’t be an issue, though it can be a bit annoying to have to turn the camera off and back on.
Though there is an electronic connection, autofocus is slow, unreliable, and can have trouble finding focus. Finally, there are some issues image with quality including a soft image and some chromatic aberration.
Description: This is one of the cheapest options for a focal reducer that has an electronic connection. If you plan on using anything besides cine lenses, this is essential. The booster itself does well to create a rather sharp image, though it’s not perfect. For the price, the extra boost in aperture is great and it is very handy to help offset the MFT crop factor.
Check the current price on Adorama (more options available).
Check the current price on Amazon.
6. Commlite Lens Adapter EF To M4/3 w/Electronic Iris And f/0.71X Speed Booster
Weight: 6.4 oz / 0.18 kg
Magnification: 0.71x
Lens Mount: Canon EF
Camera Mount: Micro Four Thirds
Strengths: The Commlite Lens Adapter is a well-built focal reducer that can add an extra 0.5 stops of aperture to your lens. This adapter has 0.71x magnification which is great for crop sensors and is an all-metal construction.
The Commlite adapter features an electronic connection as well, allowing you to change the aperture and focus through your camera if needed. The image quality is also very good for the price.
Weaknesses: While the quality is solid, using this adapter will soften your image, especially when shooting wide open. Additionally, there will be minor vignettes. Furthermore, though featuring electronic connection, continual autofocus is slow and not available in video.
Description: The Commlite Lens Adapter is one of the best affordable alternatives to the Metabones Speedbooster. Though there are some issues with a blurry image, it performs the best in comparison to many of the other budget focal reducers.
Furthermore, having electronic adaptation is extremely helpful and lets you use a variety of lenses. The all-metal build makes this adapter feel sturdy, and the image quality is very usable.
Check the current price on Adorama (more options available).
Check the current price on Amazon.
Conclusion
Often times focal reducers seem like expensive pieces of gear that aren’t worth it. After seeing some of the affordable options though, hopefully, you may be considering picking one up.
Especially for filmmakers, videographers, and photographers using crop sensors, focal reducers can greatly expand the number of lenses you have available to you as well as their usability.
Additionally, if you are transitioning between cameras, focal reducers can be a great way to equip old lenses to new cameras.
While Metabones sets the standard in terms of quality, many of these cheap options are a great foray into the world of focal reducers. Adapters such as the Commlite Lens Adapter offer solid image quality at a reasonable price and can help offset the crop factor of an MFT sensor.
There are plenty of benefits of using focal reducers, from the widened focal length to an extra stop in aperture.
If you use a focal reducer or have a favorite brand, let us know in the comments what it is and why you love it. Otherwise, it may be time to consider picking one up and testing out these devices!
Cade Taylor is a filmmaker and writer based out of Los Angeles. Originally from Seattle, he continues to work as the Outreach Coordinator for the Bigfoot Script Challenge, where he helps connect up-and-coming writers with industry professionals. When he’s not working on his own projects, helping out with Bigfoot, or covering desks, Cade loves to share what he knows with other filmmakers and promote great content.