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Anonymous
What makes a particular Leica lens a Summicron, Summilux, Elmar, Elmarit, APO-, and any other designations applying to more than one lens that I've missed?

Just curious, since the closest I've ever come to a Leica is a Panasonic FZ-8.
>> Anonymous
It depends on the optical design, series, period of manufacture, and sometimes just marketing.

Summicron refers to their standard lenses, basically the equivalent of Zeiss's Planar lenses.

Summilux refers to their line of super-fast lenses. For example, the 25mm f/1.4

Elmar and Elmarit, as far as I can tell, are the same thing but made during different periods. They are both tessar-type standard and short telephoto lens designs.

APO stands for apochromatic, meaning that the lens emploies a certain kind of correction for chromatic abberation.
>> Anonymous
Noctiluxes are f/1.0
Summiluxes are f/1.4
Summicrons are f/2.0
Elmarits are f/2.8
Elmars are f/4

Then there are the weirder ones, when the name actually referred to a specific type, like the 3.5cm f/3.5 Summaron or the 90mm f/4 (?) Hektor.

I dunno, this came out of a Leica pamphlet that I have, but it doesn't seem to always hold true.