Archived posting to the Leica Users Group, 1997/10/25

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Subject: Re: Uncoated is better ?????
From: Marc James Small <msmall@roanoke.infi.net>
Date: Sat, 25 Oct 1997 15:59:48 -0400

At 01:15 PM 10/25/97 -0400, Marvin wrote:
>  Marc - Would you please elaborate on that "performance is better in
>  low-light conditions with uncoated optics", as I can't for the life of me
>  understand how this could be since hi-speed lenses like the Noctilux
>  are designed to be used in LLC and they are coated.
>

I started with a smart-ass interpretation of "LLC" as "limited liability
company" but figured I better not.  I suspect you mean "low light conditions".

Simply put:  coatings concentrate stray light where it belongs.  Thus, a
coated lens in EXTREME low light produces black-and-white images and can
miss a subtle image.  To use a close parallel, cranking the contrast up in
the darkroom results in a win/lose situation, in which the image is either
there or it isn't.  Similarly, with an uncoated lens, the contrast is lower
and moderate images appear where, with a coated lens, they do not.

The Noctilux is designed for LOW LIGHT.  I am speaking of EXTRENE LOW
LIGHT, the sort of thing where you crank up the HP-5+ to 3200 ASA.

Marc


msmall@roanoke.infi.net  FAX:  +540/343-7315
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