[Leica] UV Filters

[sethrosner at direcway.com (Seth Rosner)]

Luis, Last year I tested a 35/2,8 Summaron and 50/2 Rigid Summicron 
(7-element) at Optikos Corporation on their Optikos OpTest Image Analysis 
System. We tested for contrast (MTF) and resolution at apertures between 2,8 
and 8, at frequencies of 5, 10, 20 and 40 line pairs/mm.
and on-axis, 12mm off-axis and 18mm off-axis.

Out of curiosity, I put a Leitz E39 UV filter on the Summaron when we tested 
for contrast at 5,6 on-axis and on the Summicron, also at 5,6 but 12mm 
off-axis. There was no discernable difference in the read-outs.
We did not check for differences in resolution.

It is my belief that if a photographer were photographing with strong light 
hitting the lens at sharply oblique angles or with an actual light source 
within the lens' field of view, the introduction of two additional lens 
surfaces (filter trailing surface and lens leading surface) would tend to 
degrade the image. And this would be more true with a wide-angle lens than a 
long lens. Otherwise, I do not believe you will ever notice a difference 
with or without a UV filter.

Also, a filter made by a reputable manufacturer should be fine. Leitz 
filters from the 1950's and 60's are splendid, provided the glass is clear 
and clean and the mounts are true. For if the filter glass is not mounted 
precisely at 90 degrees to the lens axis, then you will have reflections 
degrading the image.

Seth           LaK 9

----- Original Message ----- 
From: "Luis Ripoll (Of)" <luisripoll@telefonica.net>
To: "'Leica Users Group'" <lug@leica-users.org>
Sent: Thursday, November 11, 2004 12:49 PM
Subject: [Leica] UV Filters


>
>
> Hello all,
>
> All my life I've used a UV filter as a protection for the lenses, and
> always I've asked me three questions:
>
> 1.- Could the UV filter affect the image quality?
> 2.- In a nice glass as Leica, it should be used only Leitz filters?
> What's affect use i.e. B&W, Hoya...?
> 3.- It could be the same quality a Leitz UV from the 60's than our days?
>
> Thanks for the opinions
> Luis
>
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