How was the new family of lenses for compact system cameras (CSC) created and which steps did the lenses have to go through until they were ripe for the market?
Four years ago, a new market segment emerged in photography: compact system cameras (CSC), which are equipped with interchangeable lenses. Ever since then, compact system cameras have been the camera segment with the highest growth rates. After initially observing how the market was developing, ZEISS determined that high-performance lenses would also be interesting for customers in this market. In order to stay true to the high quality standards of the ZEISS brand, it was decided to focus on cameras with an APS-C sensor, the largest sensor that has been available so far for this type of camera. The new lenses from ZEISS should be developed for cameras from Sony and Fujifilm. The autofocus was planned from the start. Everyday photography was the class of usage defined during the early design phase, and also driven by the market, so the autofocus function was almost a must — it is a step toward higher volume market, but at the usual high ZEISS quality.
The development process began with a preliminary study by the optical designers. Experience, ‘gut feeling’ and observations from the market were fed into the first rough specifications. These were evaluated for feasibility and cost, and then had to be adapted to the production requirements. From this point on, the optical designers worked closely with the mechanical engineers. “Our goal was to translate the theoretical quality requirements into the actual construction as much as possible,” explains Program Manager Dr. Michael Pollmann, who led the development process at ZEISS. In addition to ensuring quality, an intuitive operation of the lens by the user also had to be guaranteed.
New for the mechanical engineers were the electronic functions, which resulted from the autofocus function. The motor, which takes over the role of setting the focus position, adds additional weight to the camera system. Especially with CSC cameras, compactness and light weight are decisive for the purchasing decision. The developers therefore investigated which internal parts had to be made of metal for functional reasons and where they could switch to lighter-weight materials. They finally decided to design the inner lens mechanics as a metal-plastic combination. The outer barrel is mainly of metal for reasons of durability, mechanical stability and in order to be impervious to environmental influences.
Another difference to current lenses is the electronic support of the camera’s corrective functions which corrects errors on the image afterwards. In order to be able to do that, the lens must be equipped with the function to communicate characteristics about the image to the camera.
After the optical and mechanical design was defined and the realizable quality level of the lenses determined, the next step was to convert them into prototypes. “We created various cycles of demonstration samples in order to test the concept and reach the desired performance level step by step,” continues Dr. Pollmann. A first rough sample was examined for obvious errors: Does the lens move as it should? Is there shadowing or stray light? The engineers also controlled whether the electronics were the right size and whether all their functions worked properly. These were then optimized in the subsequent process steps.
In the second prototype cycle, the image quality was controlled. To do this, the designers created various samples, sized them, and improved the mechanics step by step: “From generation to generation, we became more critical,” says Dr. Pollmann. “With the first prototype, we examined for example whether the manual focus function even worked – with later prototypes we focused on how it felt to set it. Is it rattling or does it run smoothly? What sort of noises does it make?
The approval of the prototypes is simultaneously the go-ahead sign for the pre-production. Whereas the prototypes were still being produced according to laboratory measurements, now the moment had come to verify whether the lenses, which would be manufactured according to serial production, indeed met the desired quality standards. Several weeks ago, the go-ahead for the pre-production run for the Touit lenses was also given. The Touit lenses were therefore ready for full-scale production.
The first two members of the new family of lenses are the Touit 2.8/12 and 1.8/32, both of which come with the famed ZEISS T* coating to reduce reflections and stray light.
Touit 2.8/12 – A sophisticated, extreme wide angle lens with the Distagon optics concept. Due to the Distagon design it was possible to build such a compact, extreme wideangle lens by meeting the requirements for optimum ray angles on the camera sensors. Eleven lens elements are arranged in eight groups. Two aspheric lens elements have been implemented to ensure a compact lens, despite the short focal length, of high image quality over the whole image field. Three lens elements are made of materials with anomalous partial dispersion to reduce color aberration for high contrast images with vivid color reproduction. Focusing is done by a floating elements design – all 6 lenses behind the aperture are moved.
Touit 1.8/32 – A robust and compact standard lens that relies on the tried-and-tested Planar optics concept, but which has been adjusted to the requirements of today’s digital cameras through the addition of lens elements. The additional lenses have been needed especially to meet today’s requirements for better correction of chromatic aberrations. The result is eight lens elements in five groups. Focusing happens through an overall adjustment whereby the entire length of the lens remains unchanged.
“With these lenses we have achieved our goal to address the CSC market at the high end of the market,” summarizes Dr. Pollmann. “We look forward to completing what was a long development process, and we are curious to see the pictures our customers create with the lenses.”
The Touit lenses will be available at dealers in June. A third focal length, the Touit 2.8/50 Macro, is currently in development and expected to be on the market at the end of this year. Other focal lengths are also planned.
For more information about, and specifications of, the new lenses, visit our website: http://lenses.zeiss.com/camera-lenses/carl-zeiss-camera-lenses/camera_lenses/touit/touit2812.html.