...On the Fuji X-E1 both lenses autofocused quickly enough to be a pleasure to use for street photography. But on the Sony NEX-7, the autofocus was sometimes slow enough to be a hindrance with moving subjects. When it comes to wide E-mount lenses, Sony’s very compact 18mm and 20mm optics, and even the larger 10-14mm f/4, autofocus much more quickly.
One drawback of the focusing system is that it’s noisy during both automatic and manual focus. You’ll hear it in any video you shoot unless you capture your sound with a separate device. If you do use these lenses for video, make sure your camera firmware is up to date. Zeiss says that older versions can cause autofocus problems.
- See more at:
http://www.pdnonline.com/gear/Lens-Review-Zeiss-T-8674.shtml#sthash.49yKcBHZ.dpuf