Originally Posted by Birck Cox
Just a question: in catalogs and photo articles A description of a particular lens is often accompanied by an illustration of the lens in vertical section, showing stacks of lenses singly and in groups. How am I to use that information? What can I tell about the lens? How am I benefited by knowing that it's 7 lenses in two groups?
It might tell you what design the lens falls under, Cooke Triplet, Tessar, Planar, Heliar, Sonnar, Planat/RR, etc.
But it will not tell too much about the images that lens will make in the OOF areas, and even the name might be re-used by a lens maker and applied to a lens of not of that design for more added confusion, the name "Sonnar" comes to mind