Объемистый материал по Цейссам есть у Ллойда
http://diglloyd.com/zf/index.html
но ресурс платный. 2/28 он хвалит, но про самую-самую разрешабельность не говорит. Врочем, цитирую:
Conclusions
The Zeiss ZF 28/2 Distagon maintains the same high build and image quality seen in the other lenses of the ZF line, with amazing color consistency, flare control, and very high sharpness. Its technical weaknesses include strong curvature of field (and associated astigmatism), as well as modest lateral chromatic aberration (color fringing).
An artist’s lens—in this day and age of modern optics, a prime lens with strong field curvature and strong vignetting might seem like an anachronism. The 28 Distagon will be quite unappealing to those seeking a flat field lens optimized for high sharpness on a flat plane of focus. For those looking for a lens with personality that can be mastered and exploited, the 28 Distagon will be a refreshing option. And with real 3-dimensional subjects, actual results delivered by the 28/2 are extraordinary, likely not exceeded by any other 28mm lens—so perspective should be maintained!
Resolving power (full frame high res)
Shooting a variety of images on both the 12.-2-megapixel Nikon D3 and 21.1-megapixel Canon EOS 1Ds Mark III show that that 28 Distagon has ample resolving power for any situation. It is not hard to postulate that it would maintain its high performance even on a future 30 megapixel camera. The only time that softness might be seen is when curvature of field is not accounted for eg on a flat (planar) target shot at wider apertures.