The Nikkor 5cm F1.4, 8.5cm F2, and 10.5cm F2.5 were unique optical prescriptions, followed the block diagram of the Sonnar lenses. The 8.5cm f2 was a 5 element in 3 group design, same as the 10.5cm F2.5. Both lenses were superior to the Zeiss 8.5cm f2 7 elements in 3 groups.
Same with the Canon lenses- unique glass, optically different prescriptions from the Zeiss counterparts.
They were not direct copies, they were different designs that required new optical computations.
Even the Nikkor 5cm f2 is a substantially different prescription from the wartime Zeiss 5cm f2 Sonnar "T". The Jupiter-3 is so close in prescription to the pre-war and wartime Sonnar that you can interchange the front elements and two triplets. Same with the Jupiter-8 and the 5cm f2 Sonnar. The Nikkor lenses use different optics- different relative strength among the groups. The front element of the Nikkor 5cm f2 is a stonger optic that the front of the Sonnar. Both are close enough in diameter to exchange, but "it just does not work".
This is a Pre-War Carl Zeiss Jena 5cm f1.5 with a rear triplet from a Jupiter-3:

Wide-open. The rear glass fit perfectly into the German optical fixture, and I did not have to change the shims on the lens to maintain focus.
The same trick just does not work with substituting elements on the Nikkors. I tried.
Same with the Canon lenses- unique glass, optically different prescriptions from the Zeiss counterparts.
They were not direct copies, they were different designs that required new optical computations.
Even the Nikkor 5cm f2 is a substantially different prescription from the wartime Zeiss 5cm f2 Sonnar "T". The Jupiter-3 is so close in prescription to the pre-war and wartime Sonnar that you can interchange the front elements and two triplets. Same with the Jupiter-8 and the 5cm f2 Sonnar. The Nikkor lenses use different optics- different relative strength among the groups. The front element of the Nikkor 5cm f2 is a stonger optic that the front of the Sonnar. Both are close enough in diameter to exchange, but "it just does not work".
This is a Pre-War Carl Zeiss Jena 5cm f1.5 with a rear triplet from a Jupiter-3:

Wide-open. The rear glass fit perfectly into the German optical fixture, and I did not have to change the shims on the lens to maintain focus.
The same trick just does not work with substituting elements on the Nikkors. I tried.
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