Metabones Nikon G to Micro Four Thirds Speed Booster is designed to reach infinity focus while maintaining the correct registration distance required to maintain optical quality of CRC lenses or lenses with floating elements. Both camera-side and lens-side of the adapter are made of brass, precision-machined and plated with chromium.
Reviewed by 3 customers
The other user with the detailed description hit the nail on the head. It is made of excellent build and it's perfect for my GH4 with the Sigma 18-35 ART lens. Such an amazing lens, this speed boosted adapter truly brings it and other G and F mount Nikon and Nikkor lenses to life. Tripod foot is a tad annoying sometimes as it can get in the way and kind of pointless IMHO (I mean who wants all the weight of their camera and lens to be supported solely by the lens adapter?? That's just asking for it to break.). Makes everything brighter and clearer and I absolutely would recommend this!!
Two things combine for this Speed Booster to work: 1) the smaller Micro Four Thirds sensor and 2) removing the mirror in electronic cameras like the Panasonic GH4. Removing the mirror allows the flange-to-sensor distance to be decreased. This allows physical room for adapters. The smaller sensor means a smaller circle of light is required from the lens to cover the sensor. Big lenses like FX Nikon and Canon lenses are designed to cover a big sensor. If you simply adapt them to the M43 camera, you are wasting light. The Metabones Speed Booster puts an optical element into the adapter that shrinks the big circle of light to the M43 sensor size, sort of like how a magnifying glass concentrates sunlight to a hot spot. This shrinking/concentrating of the circle of light does three things: 1) it makes the light brighter. The Nikon lens is now effectively twice as fast. An f/2.8 lens becomes an f/2 lens. Amazing. (It's the opposite of what a doubler does -- which makes the circle larger and thus dimmer.) 2) it decreases optical problems -- the lens gets sharper and aberrations decrease. (This is also the opposite of what a doubler does, which magnifies optical problems.) 3) it makes the lens wider than its indicated focal length by a factor of .72x. (A doubler has a factor of 2x, typically.) The Micro Four Thirds sensor has a crop factor of 2x -- a 50mm lens looks like a 100mm lens would on a full frame 35mm camera. So, combining all this: a 50mm f/2 Nikon lens with this adapter on a Panasonic GH4 Micro Four Thirds camera would effectively become a 36mm f/1.4 lens, but because of the M43 crop factor, double the focal length again to look like its a 72mm lens. Yeah, a little complicated. Here the formula: Actual Nikon lens focal length X .72 widening factor of the Speed Booster X 2 for the M43 crop factor. Like I said, optical magic. The adapter itself is very well built and includes a removable support foot with a 1/4-20 tripod hole in the bottom. (I had to remove it for the lens to fit the GH4 when its YAGH audio unit was attached.) It also has a ring that allows you to adjust f/stop on the lens by pushing the auto-iris lever on the back of the lens. This is especially good for the G series of Nikon lenses that don't have f/stop rings anymore. For lenses that do have f/stop rings, either shut it all the way down and use this Metabones ring or use the built in f/stop ring. But for video, the Metabones ring is clickless and silent, allowing you to change exposure in mid shot without hearing the lens click. Construction is solid. Both mounts (Nikon and M43) are chromed and smooth. I like the construction so much I also bought a normal "non-Speed-Booster" adapter ring from Metabones too. Highly recommended for either.
I use it to use my pro lenses at the GH3