Archived posting to the Leica Users Group, 1997/06/13

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Subject: Re: Noncoated filter
From: Shawn London <st942432@pip.cc.brandeis.edu>
Date: Fri, 13 Jun 97 12:09:15 -0400

At 09:46 PM 6/12/97 -0700, Jacques Bilinski wrote:
>
>Please explain how a photon reflected from the first surface of a filter
>can possibly end up on the emulsion to 'degrade the picture'.
>

It seems that it is more what does not end up on the emulsion which would 
cause the loss of image quality. If the info posted in this thread has 
been correct and that Leica lenses have 1%+ less dispersion than other 
lenses, that would mean that 1% more light is making it to the emulsion, 
ostensibly improving detail, contrast, etc.  

It would also stand to reason that a substandard filter could cause a 
host of other problems if it did not allow all light to pass uniformly 
(due to aberrations, coating, etc.) in that unevenly diffracted light 
could cause flare and so forth.