I have a GH4 with the first MFT to EF speedbooster and I’ve been very impressed. It allows the amazing GH4 to perform with great cine primes and EF stills. I just got the update that allows for autofocus and let me tell you; this is a killer combo.

The speedbooster, if you don’t know, is a reverse teleconverter that gets you more width and more f/stop (.78x and +1 f-stop) as well as being an electronic MFT to EF adapter. Previously you had aperture control in camera for EF lenses, and with the new firmware (1.7) you get AF control too.

Limitations:

  • its slower, that’s a consequence of phase detection lenses on contrast detection bodies...nothing new here
  • It wont autofocus in video mode. Bummer, but not a deal breaker
  • It doesn’t power IS in the lens (if it has it)

That being said, I’m really impressed for what it is. I’ve tried it with a 70-200 non-IS, a 16-35 L, a 24-70 L and the 100mm f.2.8 macro and they are all fast, and accurate. These were all shot and are strait out of camera in a 5 minute walkaround today. Low light is a little slower, but not much.

Very impressed with the speedbooster (original, not S or Cine) and the update. It means I can invest in Canon glass and Panasonic bodies. Win/Win.