After what felt like decades of asking for this product, Metabones finally has released a Canon EF Lens Speedbooster for Micro Four Thirds cameras like the Panasonic GH4. The Canon EF Speed booster will increase maximum aperture by 1 stop and modifies the lens view to 0.71x wider. The adapter can be powered via 5V through a MicroUSB port for the built-in electronics to change aperture values.
Unlike the RedRock Micro LiveLens Adapter which can adapt a Canon EF Lens to MFT Cameras, the aperture value has to be changed 'within the adapter'. The Metabones is a smart adapter that communicates to the lens so that aperture controls can be dialed in right from the camera as if it were using a native MFT lens. Apparently it is shipping now, and you can find out more at the Metabones website (click here).
Metabones Canon EF Lens to Micro Four Thirds Speed Booster
In regards to autofocus working, I just read a review on Andrew Reids, EOSHD website and he says autofocus doesn't work with this model.
Does anyone know if autofocus works when taking photos with a GH4?
Dennis L. Sørensen
Guess the external power is required only if you connect it to the BMCC M43 (which is passive).
Will wait for some reviews, but it really does sound amazing… seems that the aperture control alone beats any other adapters.
Out of stock already.
Yeah no power required. Great to see this speed booster finally out.
Note that ef-s lens not compatible. The canon 10-22mm is not compatible from what I read.
Cant wait to get this on my GH4.
FYI, it does not require external power as implied here; that's just an option.