There are several versions of the 120/4 mp as listed on the Zeiss site:
www.zeiss.com
Contax 645 version is 8/5 elements/groups, all the Hassy variants are 6/4. The C/Y 100/2.8 is 7/7 with a floating element. The Classic (Cosina-made) 100/2 Makro Planar is 9/8.
Yet, otherwise identical 120/4 Hassy versions ( in terms of elements/groups) have wildly differing MTF:
This is the CF:

This is CFe:


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Contax 645 version is 8/5 elements/groups, all the Hassy variants are 6/4. The C/Y 100/2.8 is 7/7 with a floating element. The Classic (Cosina-made) 100/2 Makro Planar is 9/8.
Yet, otherwise identical 120/4 Hassy versions ( in terms of elements/groups) have wildly differing MTF:
This is the CF:

This is CFe:
