Re: [Leica] 50/1.2 or 50/1.5 or 50/2?!

[Krechtz@aol.com]

In a message dated 8/4/00 7:33:33 PM Eastern Daylight Time, dante@umich.edu 
writes:

<< I suspect the old Canon transmits more light, even stopped down, even
 without multicoating and LD glass.  Or it's really a 1.2 and the f/2
 mark is where 1.5 really is. >>

I used to ponder questions like these.  I have had similar experiences.  The 
first thing to remember is that f/stops are not absolutes but arithmetically 
derived constants.  Translating them exactly into optical and mechanical 
operational terms requires a high degree of precision.
Some years ago, I found Sherry Krauter herself working away at a table at a 
large camera show.  I asked her a question similar to this one.  Her position 
at that time was that even the best quality control practices employed during 
that era left plenty of margin for error, by today's standards.  
I have never since thought to find absolute answers to such questions, 
including those relating to which lens in a given class was better than 
another.  I have generally come around to her point of view.  However, I have 
seen remarkably little variation from unit to unit among vintage Leitz 
lenses, considering the complete absence of computers in design and 
manufacture.
When I have encountered lenses that behaved unexpectedly, I have simply 
adjusted the aperture ring to compensate and forgotten about the cause.  
Sherry did me a favor.  Essentially, she told me to forget the details and 
just enjoy shooting.

Joe Sobel