If you've got Canon EF or EF-S glass but have migrated over to Micro Four Thirds or Sony e-mount mirrorless, the DEC LensRegain is one of the smartest ways to simultaneously up your production values while retaining your investment in the glass. If you think of it as a mashup of a Metabones Speedbooster-style focal length reducer and a wireless follow focus controller that uses the motors already inside those Canon lenses themselves - plus, hey, why not -- aperture control, you're spot-on. It's one-third the price of something like the Cinegears wireless follow focus system because Aputure was very smart and very focused -- but even with something this good, it won't be as smooth as what you can achieve with a real geared, manual focus cine lens. Then again, your audience may not be able to see the difference, even if you can. Best to use STM lenses.