I just downloaded and installed a firmware update on my Metabones IV adapter. Firmware update V0.41 for EF-E Smart AdapterTM MARK IV After downloading and updating the adapter I did a quick test with my Canon 300 F4L IS. Previously this lens would not adjust aperture or support IS. With the new firmware both appear to be working. I'm going to do some more testing tomorrow. If it indeed is a reliable update I am going to be very happy. I liked the 300 on my 5DIII and was disappointed when it wouldn't work at other than max aperture with the Metabones IV. This was with an A7II not sure about other camera bodies.