[Leica] Internal lens coatings.....

["BIRKEY, DUANE" <dbirkey@hcjb.org.ec>]

>
>Why I speak of the front and rear outside surfaces and coating, is 
because
>I have a Leica document (it's here somewhere) that said that when they
>developed some of their special glass, they did not coat the internal 
lens
>surfaces, they only coated the external (front and rear) surfaces. They
>said that the glass had such high transmittance, that no coating would 
help.
>
>This is in a fairly old document, and I cannot, at this very moment, 
come
>up with it. But I know it's here in my library and would be happy to 
send
>along the reference when I do come across it again.
>
>Jim

The key words in the above paragraph are "some of their special glass".  

If you want to know whether the lens elements in your favorite lens or 
coated or not.....hold it under a bright light and move it slowly from 
side to side..... anytime you see a white reflection you'll know you have 
a uncoated surface in your lens.  Supposedly you can tell the thickness 
of the coating etc. by the color of it etc..... but I've long forgotten 
that rather useless piece of information.

My 35 and 50 Summicrons appear to have two uncoated surfaces (the two 
uncoated surfaces are on different elements in each case, that is to say 
that one side of the element is coated and the other is not).    There 
might be one uncoated surface in the 90.

Duane Birkey

HCJB World Radio
Quito Ecuador