Touit Optics: Manual / Autofocus, Lens Design
The Zeiss Touit lenses for Sony NEX and Fuji X are reviewed in depth in Guide to Mirrorless.
May 2013 Q&A from Carl Zeiss Inc.
Why does this lens family feature an autofocus (AF), while the SLR lenses only have a ￼manual focus (MF)?
The development of autofocus lenses requires close collaboration with the camera manufacturer in order to ensure full compatibility with the pertinent camera system.
In its collaboration with Canon and Nikon, ZEISS currently is not even licensed to use the autofocus interface on the camera. Therefore, we are concentrating on offering the best manual focus lenses for these systems.
In its collaboration with Sony, ZEISS is developing autofocus lenses for the Alpha and NEX systems. The new Touit lenses are also available for the Fujifilm X system. ZEISS and camera manufacturer Fujifilm worked together closely on this project.
Does this mean that there will also be SLR lenses from ZEISS with an autofocus?
There are AF lenses from ZEISS for the Sony Alpha system. Because of the patent situation, it is not currently possible to offer a ZEISS AF lens for the other camera systems with EF and F mounts
Is the manual focus on the AF lenses a "true" manual focus like that on the SLR lenses?
As with all lenses for the Fujifilm X and Sony NEX systems, the ZEISS Touit AF lenses feature an electronically coupled focus ring. Nonetheless, we have done our utmost to make manual focusing as precise as possible.
Will the lenses be manually focusable?
The Touit E mount lenses for Sony NEX cameras and Touit X mount lenses for Fujifilm X cameras can be precisely focused manually thanks to their large focus rotation angle. This requires the user to switch to manual focus on the camera housing.
On the Touit lenses, why is only the X mount model equipped with an aperture ring?
The X mount lenses for Fujifilm X cameras feature a manual aperture setting option on the lens because the design of this system does not accommodate an aperture setting feature on the camera. The aperture setting for the E mount lenses for Sony NEX cameras can only be configured on the camera due to the design.
Why don't the lenses feature image stabilization?
The Touit 2.8/12 and Touit 1.8/32 lenses do not feature image stabilization. With shorter focal lengths, stabilization is not necessarily required and can even impair the imaging performance of the lens. For quality reasons, we have therefore decided to offer these lenses without image stabilization.
What lens design is used for Touit? How many lens elements?
The lenses have an entirely new optical and mechanical design that takes into account the special requirements of mirrorless CSC cameras. The Touit 2.8/12 has 11 lens elements in eight groups. The Touit 1.8/32 has eight lens elements in five groups.
What type of AF motor is used on the lenses?
ZEISS Touit lenses feature DC gear motors with an iron-free core for automatic focusing. These motors are highly efficient and can accelerate quickly.