I am not aware of Carl Zeiss Jena ever making a zoom lens of that focal range.
However there are such Carl Zeiss zoom lenses (Vario-Sonnar 28-85mm). Be aware of the existence of two different Zeiss companies in both parts of Germany.
There are parfocal zoom lenses that keep focus during zooming once focused correctly.
The early zoom lenses were built up to the varifocal principle and do not keep focus.
May that be the reason?
Last edited by AgX; 03-20-2013 at 06:56 AM. Click to view previous post history.