In what sense is the 38mm f2.8 Sonnar on the Contax T or T2 a Sonnar lens?

[alfu]

I am just after a bit of history of the lens design of the contax T or T2. The classic sonnar design is 7 elements in 3 groups (https://en.wikipedia.org/wiki/Zeiss_Sonnar) but the contax is 5 elements in 4 groups. So what characteristics are inherited from the classic sonnar design? For example, is the famed bokeh and transition to OOF areas preserved?

 

[02Pilot]

Look further back into the history of the Sonnar and you'll find the Ernostar design. This is helpful in understanding the later derivatives that diverge from the classic 6/3 or 7/3 Sonnar formulae.

 

[alfu]

Ah thanks!

https://en.wikipedia.org/wiki/History_of_photographic_lens_design#Ernostar_and_Sonnar

Still, how close is the 38mm f2.8 to these old designs?

 

[02Pilot]

Pretty close from what I've seen. Search for Ernostar and Contax T lens block diagrams and you'll see considerable similarity. Same goes for the Nikon 35/2.8 in the L35AF - there's a good Nikon historical piece on the development of that lens floating around on the web somewhere.