One of the key functions to note about this lens is its Internal Focusing (IF) which enables focusing without changing the length of the lens barrel. With the Silent Wave Motor (SWM), the lens is capable of achieving high-speed autofocusing with exceptional accuracy. Both technologies provide Mikko with powerful and quiet operation.
“The autofocus is fast and works accurately in the situations I have used it. If you are primarily using the lens for photographing the stars, you might want to learn when it is focused to infinity either manually, or with the autofocus in vast landscapes. If there is a small light source in the scenery, the lens can focus to it in most of the cases. In pitch-black situations, I recommend using the manual focus. Thanks to its Silent Wave Motor, autofocus operations are fast and almost silent.”