Re: Identical optical formula - indentical quality?

[Graywolf]

I think that a point needs to be made about these so-called optical formulas 
(actually optical diagrams). Two lenses can be a classic tessar layout but not 
at all similar. All you know for sure is that they would both have 4 elements in 
three groups. The refractive indexes could be different, the curves different, 
the types of glass different, the spacing different, etc; but both would show 
the same optical diagram.

So a general answer to Peter's question is, "who knows?". Only by disassembling 
each lenses and checking the exact optical characteristics could we know for 
sure whether they were the same or not.

graywolf
http://www.graywolfphoto.com
"Idiot Proof" <==> "Expert Proof"
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Peter Smekal wrote:
Hi everyone,
browsing Bojidar's K-mount site I wonder: Sometimes F and FA lenses have
what looks like identical "optical formulas". Would you say that for
instance the F 135/2.8 [IF] and the FA 135/2.8 [IF] also have identical
optical quality?
Thanks,
Peter Smekal
Uppsala, Sweden