This Sonnar lens is of a traditional lens design that has been around a long time but, in this case, its formulation has been greatly refined, increasing its speed and reducing lens aberrations to very low levels, providing high contrast and sharpness out to the corners of the image field even at full aperture.
The picture below shows the capability of the lens to render micro contrast and detail in a subject plus the typical Zeiss 3-D pop.
The film used was Kodak Portra 400 renown for its fine grain and helping to keep contrast under control a on a very bright, sunny day. You can see that this lens is typically a Sonnar with no detectable distortion in any of the images exhibited here (or taken with it on any subject at all for that matter).
You can hurt you eyes trying find any unsharpness in the original images (i.e. negatives in my case) let alone the crappy (when compared to the analogue originals) high res scans even wide open all away across the image field, because there isn't any. Remember this is from the native media image direct from the lens itself, there is no in-body digital processing trickery going on as the lens works on Contax G analogue film cameras.
Finally I am fed up of hearing the myth perpetuated that the lens is affected by the fact it cannot be focused accurately on Contax G2 cameras, especially close up or on moving subjects.
This is rubbish. All the failures to focus problems I have seen have been down to operator error due to sloppy focusing technique or failure to take the time to understand how the electronic rangefinder AF system works which is uniquely different to anything else out there.
So as you can see from the pictures above, all in all the Carl Zeiss Sonnar T* 90mm f2.8 is a lovely bit of glass.