Metabones has begun shipping yet another of their Speed Booster converter/adapters, and I haven't been mentioning the individual shipments as they occur, so it's probably worthwhile to bring you up to speed on what's now available and shipping:
- Fujifilm XF mount: Alpa to XF, Contarex to XF, Yashica to XF, Leica R to XF, Nikon G to XF
- m4/3 mount: Yashica to m4/3, Leica R to m4/3, Nikon G to m4/3
- Sony NEX mount: Alpa to NEX, Canon EF to NEX, Contarex to NEX, Yashica to NEX, Leica R to NEX, Nikon G to NEX
As a reminder, the Speed Booster is a lens adapter with built-in optics make the lens .71x lower in effective focal length and one stop faster in maximum aperture. To use one common example, many Fujifilm X-Pro1 and X-E1 users are formerly Fujifilm DSLR users, and those used the Nikon F-mount, so those users very well may have some Nikkors sitting around. They can continue using those Nikon lenses by using the Nikon G Speed Booster, and the adapter even addresses the crop factor problem. For example, a 50mm Nikkor would be effective 75mm on the XF cameras' 1.5x APS sensor. But the .71x correction makes the lens perform like a 35.5mm lens, which is 53mm effective, or very near the marked focal length.
While the Speed Booster adapters are expensive, after using one for awhile, I find that they have a place in my bag. They're not the perfect solution that many claimed they would be after reading the original marketing material. But I'm reasonably impressed with what they do. A focal reducer such as the Speed Booster, when done right, does have real benefits.