Tessars and triplets?

[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?

 

[xayraa33]

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🙂

 

[David Hughes]

Hi,

Welcome aboard.

I think the answer is that a lot of people like technical details, even though they don't or can't use the information. And lenses aren't the only area where this info is given; look at car catalogues and so on.

Regards, David

 

[p.giannakis]

Taking apart a lens to clean it and not sure how to put the elements back? Those illustrations can help (happened to me once with a Zuiko).

 

[tunalegs]

If you're looking at older lenses these cross sections can provide important information. I recently repaired a camera with an Aldis Uno lens. It's a triplet with three elements in two groups, two elements being cemented together. Since it is uncoated, this is important because it means there are fewer glass to air surfaces than in the more common Cooke triplet type which has three elements in three groups - air spaces between each. Fewer air spaces mean less internally reflecting light, and therefore higher contrast.