Canon may be working on adding an aperture ring on future EF lenses, which the patent dubs as a “diaphragm driving unit”, for more fluid control of the iris while recording video. Currently, any on-the-fly changes to the aperture cannot be made smoothly, because adjusting it is done on the camera body.
In a move that is essentially a throwback to Canon’s earlier FD and FL lenses, the new design however will use electronic control as opposed to a mechanical approach. Moreover, according to the patent, it seems as if aperture adjustment on the lens is only available during video recording, as still images will still require changes to be made on the camera body, as is the current method.
To view the complete published patent, go HERE.