Re: [Leica] For your information...

[Jan or Lee <lhermann@wavecom.net>]

Dear Seth,
         Does this mean that we can expect a Viewfinder article exploring 
the resolution of the Dual Range Summicron with MTF curves for f-stops 
smaller than f/5.6?
I enjoyed your opinion in the past, thanks.
Lee



At 09:54 PM 1/8/2004 -0500, you wrote:
>----- Original Message -----
>From: "Don Dory" <dorysrus@mindspring.com>
> > John,
> > Thanks for the link.  I guess for rangefinder users that just about
> > settles the question for 1A or UV filters unless there is a specific
> > need like saltwater, sand, two year olds with peanut butter
>
>It does, Don,  if there is a light source in or near the viewing angle as is
>obvious in three of the four images. And depending on the aperture.
>Otherwise, I am not persuaded. Recently while testing a dual-range Summicron
>(yeah, yeah, you know me!) on an EROS MTF apparatus, just after running the
>MTF curves at f/5,6 and 12mm off-axis (the height of the near edge), out of
>curiosity I put on a Leitz E39 UV filter. I did it off-axis because on-axis,
>the light beam is of course directly through the center of the lens and much
>less likely to flare or degrade the image. The curves without and with
>filter were absolutely identical. If there were not a ruling from on high -
>and a correct one - that one cannot attach files to a LUG post, I would show
>you the curves. Incidentally, the contrast of the dual-range at f/5,6 at the
>critical (according to E.P.) 20 and 40 lp/mm is at least as good as that of
>the current 50/2 Summicron whose official MTF curves I have inspected.
>
>That said, I would still not use a UV filter in available light conditions
>nor outdoors unless physical damage were a risk, Don's mentioned saltwater,
>sand, 2 yearolds etc.
>
>P.S. at 2150 here in the foothills of the Aridondacks (sic) the thermometer
>temperature is a springlike -20 C. and almost everything is white.
>
>Seth                  LaK 9
>
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