[lars_bergquist]

The recomputation was no less important than that which changed the collapsible 50mm Summicron into the rigid type, and these are counted as two different version. Both were of course modified seven element double Gaussian types and their lens diagrams do look superficially very similar. Both the early 90mm Summicrons are six element classical double Gaussian designs (1–2 : 2–1) and such lenses have been thick on the ground during the entire twentieth century.

There is more to lens design than a simple lens layout diagram.

The old man from the Age of the 3.5 Elmar