[Leica] Lens coatings

[Jim Brick <jim@brick.org>]

Frank,

Since I'm not an optical engineer, I only have the knowledge that I gleaned
from reading. I accept your explanation below as it is obvious that you
know a lot more about this than I.

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.

Thanks for the optics lesson,

Jim

At 06:29 AM 12/9/98 -0500, you wrote:
>Jim Brick wrote
>
>>Could be... But I suspect that it's the front element coating more than<
>>anything. That is, BTW, the first line of defence against flare. And
>since<
>>the flare occurred with bright objects or stray light hitting the front<
>>element, I'm convinced that it is a coating problem.<
>
>Sorry Jim, you have IMHO got this COMPLETELY the wrong way round. There are
>a number of parameters affecting flare, the most important being the
>geometry of the lens (number, position and shape of elements). There are
>vrious ways of reducing the flare caused by these design limitations. These
>include baffles, antireflection coatings on internal surfaces and surface
>coating of the lens elements. If we just consider the lens element coating
>the LEAST important coat is that on the outer surface of the front element.
>The most important are the coatings on closely spaced and/or highly curved
>internal elements.
>
>...
>
>Best regards
>Frank
>