According to their marketing material, this adapter promises to reduce the focal length of some of the legacy lenses while brightens the lens (by a full stop)! On top of this, apparently, you get sharper images! The Metabones adapter works by applying x0.71 magnification to the legacy lens, hence you are essentially compressing the image.
Apparently, this technology has been used for a long time in telescopes. The same technology works in mirrorless cameras because of their short flange distance (that’s the distance between the lens mount to sensor). This allows the addition of focal length reducing optics to the space within the adapter between the lens and camera body. They call this a “telecompressor”.
Here’s some visual diagram that shows how this compression works:
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As you can see, you can only use either FF or APS-C lenses on MFT bodies. Most lenses are sharper in the center area – perhaps this plays a role in raising the sharpness? Not sure.
Look at the possibilities:
- A legacy 135mm f/2.0 lens would convert to 190mm equiv. f/1.4!
- A legacy 100mm f/2.0 lens would convert to 140mm equiv. f/1.4!
- A legacy 70-200mm f/2.8 lens would convert to 100-280mm equiv. f/2.0!
This all sounds too good to be true. It will be interesting to see some real reviews on this adapter.
There are couple of known cons as well. Although the adapter is expected to support auto aperture and IS, you will only have a manual focus.