Archived posting to the Leica Users Group, 2009/10/08

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Subject: [Leica] Zeiss Normal 50mm f/2 Planar T* ZM
From: mark at (Mark Rabiner)
Date: Thu, 08 Oct 2009 20:23:59 -0400

> Frank Filippone wrote:
>> Makes no difference to the cost of the blanks.  A chunk of glass of type 
>> ABC
>> is the same, regardless of the grinding yet to be done on it.  Yes, the 
>> cost
>> of making those blanks into a finished lens element may/could/probably is
>> different.
> Company A can specify glass type ABC with tolerances for refractive index
> +-0.2% dispersion +-0.25% surface hardness +-0.3% expansion coefficient 
> +-0.7%
> and company B can specify the same glass type with tolerances 1/2 of 
> company
> A's requirements and I'll bet company B's glass blanks are gonna cost more 
> and
> the finished lenses will show a lot less sample variation.
> Doug Herr
> Birdman of Sacramento
And there's glass which isn't even glass. Fluoride whatever. Its also good
for your teeth.
And glass which is ground using sophisticated methods hence our ASPH's
starting with the 24 2.8 made with the Schneider machine and other methods
first by hand costing thousands. But then using molding methods which was
ahead of its time but in the end  perhaps did not work out.

By Frank is right glass is glass they'd save money just taking the window
panes out of the windows and using those.

Mark William Rabiner

In reply to: Message from wildlightphoto at (Doug Herr) ([Leica] Zeiss Normal 50mm f/2 Planar T* ZM)