CP+ 2015: Sony shows off new technology
CP+ 2015: Sony Stand Report
We were curious about the advantages of the new autofocus motor in the FE 35mm F1.4 ZA, and Sony engineers pointed us to this display showing details of the Direct Drive SSM (Super Sonicwave Motor) technology included in this new lens. As we mentioned, Direct Drive SSM is based off of technology used for in-body image stabilization. A piezoelectric element that translates an applied electrical field into mechanical movement is used for precise linear positioning of the focus group. Piezoelectric actuators have been extensively used in many applications for precise, linear positioning, so it's exciting to see applied to autofocus. The small Direct Drive SSM (the horizontal rod with a cap in the picture at bottom right) also allows for a smaller lens barrel than what would have been possible with, say, a ring-type motor.
We were able to try out Sony's '4D' continuous AF with this lens on an A7 II, and it was, frankly, jaw-dropping impressive. As long as our subject stayed within the phase-detect area of the frame, horizontal, vertical, and depth tracking was incredibly accurate, fast, and completely silent for an erratically moving subject. Almost every shot was tack sharp on the intended subject matter at F1.4. In good light, we wouldn't be surprised if this combo gave top-of-the-line DSLRs a run for their money when it comes to continuous AF with subject tracking (automatic AF point selection to track an initially chosen subject across the frame).