Metabones recently updated their Canon EF to Sony E-Mount Smart Adapter IV to Metabones T Smart Adapter IV ($399) with improved anti-reflective internal coatings. According to Metabones’ website, “Enhancement on new MARK IV (MB_EF-E-BT4) vs. old MARK IV (MB_EF-E-BM4): The inner hole is painted with flocking material coating. This can further reduce the internal reflection.”
I tested both my original Metabones Smart Adapter IV and the new Metabones T Smart Adapter IV, both running fw 0.41. (Both versions have a USB port for firmware updates.) My tests verified this to be the extent of the improvement. The anti-reflective interior coatings are indeed “blacker” – but the AF performance was identical will EVERY lens I tested.
The Bottom Line
If you’re happy with the anti-reflective capabilities of your current Smart Adapter IV – there is absolutely no AF performance gain by upgrading to the new “T” version. But if you’re buying new, make sure you get the new “T” version.