Metabones Speed Booster adapter gives lenses an extra f/stop and nearly full frame focal lengths on APS-C sensors - Newsshooter
Metabones T CINE Speed Booster ULTRA 0.71x (5th Generation) - Canon EF to Sony E-Mount Adapter | Lens / Mount Adapters | Lenses / Accessories | Buy | AbelCine
What is the Metabones Speed Booster? - YouTube
Metabones introduces Speed Booster series for Blackmagic Pocket Cinema Camera: Digital Photography Review