The Metabones Speed Booster generated a lot of buzz when it was first announced earlier this year. It is not just another lens adapter for mirrorless interchangeable lens cameras (MILC). What sets this apart from normal lens adapters is its ability to provide a full-frame/near full-frame field of view and shallow depth of field. On top of that, you also gain a full stop of light, which means that if you are using a Nikon 24-70mm f/2.8 zoom lens, your effective aperture is now f/2.0! Sounds like magic, right?

Actually, it just involves physics, as we explained in our previous article on the Metabones Speed Booster. Although it may sound like a bad idea to put another glass in between your lens and your sensor, the 4-element glass optics is actually designed by Caldwell Photographics, a photographic company that designs and develops glass for professional and consumer lenses.

How the Speed Booster Works

So here is a quick recap on how Speed Booster works: Normally when you mount a full-frame lens unto a cropped sensor MILC camera, only a portion of that lens’ light is actually being utilized by the cropped sensor. On the other hand. the Speed Booster’s glass focuses all the light that covers a full-frame sensor into a cropped sensor. So not only is the cropped sensor receiving more light information, but that light is more intense, resulting in a brighter aperture gain of one F-stop. In other words, the Speed Booster essentially works like an “inverse” teleconverter or a more accurately, a focal reducer.

This light focusing effect also decreases depth of field (DOF) and field of view (FOV) by a 0.71x crop factor for that lens. The formula to find how the adapted lens will look on your MILC is simple. You simply multiply the focal length of your lens by 0.71x, then multiply the answer by your sensor’s crop factor. So let’s take a look at how a 50mm will look on two MILC, the Sony NEX-6 (1.5x crop) and the Panasonic GH3 (2x crop).

50mm lens x 0.71x = 35.5mm focal length
Sony NEX-6 (1.5x crop factor): 35.5mm x 1.5 = 53.25mm
Panasonic GH3 (2x crop factor): 35.5mm x 2.0 = 71mm

If you really want to learn the in-depth technical details of the Speed Booster, you can read the Speed Booster white paper.

Now that we got through the math portion of this review, let’s take a look at how well the Metabones Speed Booster actually perform in real life. For this review, I paired my Panasonic GH3 with the Speed Booster Nikon G to mu4/3 adapter. Here are the lenses that I used:

Nikon 50mm f/1.8 G
Nikon 70-200mm f/2.8 G

Other lenses that I have used and will be talked about in upcoming articles include the Nikon 24-70mm f/2.8 G and the amazing Sigma 85mm f/1.4 prime lens.

The Metabones Speed Booster

The adapter itself is very compact and it is about as thick as the Panasonic 20mm f/1.7 or the Canon EF 40mm f/2.8 STM pancake lens. The build quality is definitely rock solid, and the fit and finish feels superb. In fact, thanks to the all-metal mount on both sides, when you mount a Nikon lens to the Speed Booster or the Speed Booster to a mirrorless camera, there is no give, play, or flexing. All the connections just feel secure. The 4-element glass is also high quality, and comes clean and scratch free.

Since this is the Nikon version, there are no electronic contacts, which means that you must manually focus all of your Nikon lenses. Only the Canon EF to NEX Speed Booster adapter features electronic contacts and electronically adjustable aperture and AF.

The adapter can mount both Nikon F and Nikon G lenses, and while the Nikon F lenses have their own aperture ring, the Nikon G lenses’ aperture is controlled by the Speed Booster’s aperture ring that mechanically connects to the Nikon G lenses.

Studio Test Setup

In order to test the Speed Booster, I paired the Speed Booster with the Nikon 50mm f/1.8G and the Nikon 70-200mm f/2.8. The Nikon 50mm becomes a 71mm full-frame equivalent and the closest native lens that matches that focal length is the Olympus 45mm f/1.8, which has a 90mm full-frame equivalent. For the 70-200mm f/2.8, I matched it against the superb Olympus 75mm f/1.8 (150mm ff equivalent), and set the Nikon to 105mm, which gives it a 149mm ff equivalent. The camera is mounted on a tripod and each image is shot on a 2-second timer.

One thing to note that there is some exposure inconsistency in the way the Aperture ring work on the Metabones Speed Booster that I will explain in a little bit. As a result, instead of giving equivalent f-stops from the Speed Booster, I will note the F-stop markings on the from the Speed Booseter’s aperture ring instead.

Here is how it looks like wide open with the Olympus 45mm f/1.8 lens at f/1.8:

And this is the image looks like with the Nikon 50mm f/1.8G wide open. Notice that that it now has a wider field of view:

This is how the image now looks once I moved the camera and tripod closer in order to fill the scene with the basket.

For the Nikon 70-200mm f/2.8, I set the focal length to 105mm, which will give me 149mm FF equivalent that matches the Olympus 75mm’s 150mm FF equivalent. This is how both setup look with the Olympus, followed by the Nikon.

The Olympus 45mm f/1.8 and the Olympus 75mm f/1.8 are two of the sharpest lenses in the micro 4/3 lineup. So how does the Metabones Speed Booster, the Nikon 50mm f/1.8G, and the Nikon 70-20mm f/2.8G stack up?

The Pros

Noticeably Sharper Center at Wide Open

There is a definite difference at the focus point, which is the three brass buttons on the leather strap underneath the basket handles. The Speed Booster + Nikon 50mm (right image) delivers a much sharper image with better contrast.

The Olympus 45mm doesn’t really match the center resolution of the Speed Booster until f/5.6:

After f/8.0 for the Olympus 45mm and F4 for the Nikon 50mm, diffraction starts to set in.

As for the Olympus 75mm f/1.8 and the Nikon 70-200mm f/2.8, at wide open, the Nikon is almost as sharp as the Olympus. Not too bad for a zoom lens.

At f/2.8 for the Olympus and F2.0 for the Nikon, Nikon has the slight edge in sharpness and contrast:

Things do turn around for the Olympus at f/2.8 where it starts to match overtake the 70-200mm. Still, though, not bad keeping up with the sharpest lens in the Micro 4/3 lineup.

Shallower DOF
Just as promised, the depth of field is shallower when using the Metabones even though the Olympus has the focal length advantage (90mm FF equivalent vs 71mm). The bokeh quality of the Nikon and Sigma lenses that I tried is simply gorgeous, and with the Speed Booster, they are easier to create.

Olympus 45mm at f/1.8

Nikon 50mm at F1 (wide open)

Olympus 45mm at f/2.0

Nikon 50mm at F1.5 (1/2 stop down)

The sports figure does not become sharp until f/11 for the Olympus 45mm and F5 for the Nikon 50mm.

In this next example, the Nikon 70-200mm f/2.8 at f/2.8 (F1) is almost as shallow as the the Olympus 75mm f/1.8 at f/1.8.

The Cons

Manual Focus Only

With the Metabones Speed Booster, a full-frame lens becomes shallower, gains a stop of light, and becomes sharper in the center. So what are some of the drawbacks of the adapter. With the exception of the Canon EF, none of the Speed Booster feature auto-focus, which may take some getting used to for photographers not accustomed to shooting with manual focus. Most likely, your workflow will slow down quite a bit, especially if you love to shoot with wide apertures.

The good news is that the GH3 and many mirrorless cameras allow you to zoom in for fine focus-checking. The bad news for at least the GH3 owners is that the GH3 still does not offer focus peaking, unlike its younger sibling the Panasonic G6 or competitors like the Fuji X-E1 and the Sony NEX-6.

F-Stop and Aperture Change with Built-in Aperture Ring is Not Linear
This is actually an issue I noticed when I started recording down the aperture and shutter speed for each aperture change. The ISO stay constant at ISO200. The aperture ring is designed to increase by 1/2 stops for every hash mark. I shot all the lenses in Aperture Mode in order to have remove potential human error in judging exposure.

Instead, what I discovered was that the shallower aperture range (F1-F4) increases a lot more than the narrow aperture range (F5-F8). For example, instead of having just a one-stop difference between F1 to F2 on the aperture ring, I recorded a 2-stop change as my shutter went from 160sec to 40 sec.

Between what is supposed to be a 3-stop movement of F5 to F8, there is very little change exposure as indicated by the shutter speed change from 0.3 seconds to only 0.6 seconds.

I contacted Metabones and had several e-mail conversations in my findings. It turns out that the main issue with this non-linear aperture change is the aperture mechanism of Nikon lenses. The engineers found that among different Nikon lenses, there may be up to 1 stop difference between difference lenses, even though the aperture lever is set to the same position. Nikon bodies can talk to the lenses and work around this, but third party adapters run into problems.

The engineer said there are two ways to handle this problem:
1. Have an aperture ring with short throw and direct coupling. The user can only select “Full open”, “Fully stopped down” and “Somewhere in- between”. Adapters from Kenko, Novoflex, etc. work like that.
2. Have an aperture ring with a large movement (similar to a normal Nikon aperture ring) and have many nice click-stops approximately at every F-stop. These click-stops cannot be accurate for all lenses at the same time.

They chose to utilize the second solution even though it is more complicated and expensive. For lenses that have their own aperture rings, this should not be an issue. The Nikon G lenses are the lenses that may be affected.

Not Very Sharp Around the Edges With Large Aperture

Although the center and the areas around the center are sharp, there is a noticeable drop in resolution and clarity as you get closer to the edge of the frame. You have to step down by about 3 to 3 1/2 stops (F3-F3.5 on the Speed Booster aperture ring) before the edges becomes as sharp as the rest of the picture. On the bright side, the drop in image quality is nowhere as bad as the Vizelex version of the Speed Booster. The blurred quality doesn’t display severe blooming, vignetting, aberration, or color shifting. It is actually pretty hard to see the drop in sharpness when the image is only web-size quality.

(Olympus 45mm left image, Speed Booster+Nikon 50mm right image)

Conclusion

After this studio test it is safe to say that the Metabones Speed Booster performs very well in regards to increased sharpness in the center, shallower DOF, a gain in aperture stop, and overall image quality.

So far, I really like the Speed Booster despite some of its issues. As long as you can get comfortable with manual focusing and you have some good set of Nikon lenses, the Speed Booster can be an excellent lens adapter to have around with you.

In the upcoming articles, we will take the Speed Booster to some test shoots to see how well it will perform in both natural light and strobe environment. Just as a sneak peek at the potential for portraits, take a look the pair of eyes below as taken with the Speed Booster and the amazing Sigma 85mm f/1.4 prime lens. Stay tuned for more testing!

Image Straight out of Camera