Finally, the first auto focus lens I buy and use in my life, and happens to be the hot from oven Zeiss Batis 135/2.8 Apo Sonnar T* for Sony FE mount. Full frame, Apo design, auto focus!
Below is a simple illustration of the evolution of Zeiss 135mm f2.8 over the years, less the very respectable Contarex 135/2.8 Sonnar.
From left to right:
Rolleiflex HFT 135/2.8 Sonnar, Contax 135/2.8 Sonnar T*, Zeiss Batis 135/2.8 Apo Sonnar T*.
Roughly to scale. Weight: Rollei-450g, Contax-585g, Batis-614g.
In old days Zeiss lens designs are always very elegant, making use of very few lens elements and groups. From an engineer point of view the simplest design is the best and most elegant design. But today with very high resolution digital sensors even Zeiss will need to make their design fairly complicated to cater for much stringent performance requirement and the do-not -quite-make-sense pixel peeping on the computer screen. For telephoto the unavoidable CA and colour fringing, and for Batis design for auto focus. Thus you can see the fairly complicated Apo Sonnar design for the Batis series, and knowing Zeiss has been very stingy on labelling their lens as Apo you would thus expecting very high standard of correction for the Batis 135/2.8 Apo Sonnar, and of course with the renown T* multi-coating. Based on the lens diagram I think the Batis Apo Sonnar is no longer a conventional Sonnar design, as the design now need to cater for very high correction of images and also internal focusing for auto focus. The lens design used floating elements, but Zeiss only uses special glasses for this lens and no aspherical elements to achieve the Apo quality.
The one of a kind O LED distance and depth of field indicator,
visible when attached to the camera with the camera power on,
selectable for visibility for manual, auto focus or both modes.
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