A recent question about the naming scheme adopted for Carl Zeiss lenses encouraged me to do a little research. So I wrote the first version of this article... but then I couldn't stop reading about lens design! So now you can enjoy an entire series by clicking on the banner above.
Creative names like Planar, Sonnar, and Tessar were initially used to describe families of optical designs. But later they were used for marketing reasons, so the original meanings were not always preserved.
I now have more detailed articles on the development of lenses in the nineteenth century and those that used the symmetrical pattern. This article repeats some of that information, but from the perspective of Carl Zeiss offerings, in particular the Contax-Yashica line. (Since these are personal favourites.)