Archived posting to the Leica Users Group, 2002/03/09

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Subject: [Leica] Rangefinder Whiteout Problem - The Answer from Leica
From: Dr.Alexander.Kraus@gmx.de
Date: Sat, 9 Mar 2002 10:26:44 +0100 (MET)
References: <MBBBJHIBKCKEAEOKKBPOKEHHCMAA.bdcolen@earthlink.net>

Hi Lugers,
much has been speculated about the rangefinder flare problem in late M4-P
and M6 (TTL)
cameras. Recently, I found an interesting posting in the Leica customer
forum, where someone stated that the reason for the whiteout of the rangefinder
patch would be the switch from a flat mirror (for brightline illumination) to
a parabolic one. The latter one would give siginifcantly brighter frames,
however under certain light conditions, the light would be focussed directly on
the rangefinder hole of the frame mask mechanism.
This sounded very reasonable to me and so I decided ton ask Leica directly
whether above explanation is correct. Yesterday, I received an email from Mr.
von Gyimes from Leica. He wrote: (Translation behind the citation) 

"Die Erklärung mit dem parabolischen Spiegel stimmt. Unter
bestimmten ungünstigen Lichteinwirkungen (ca. 110° zur Lichtquelle) 
kann der Entfernungsmesserfleck völlig weiß und unbrauchbar werden. 
Dieses Problem ist mit der zweiten verspiegelte Fläche am 
Suchereinblick der Leica M7 und auch M6 TTL bereits deutlich 
verbessert worden, konnte aber noch nicht ganz ausgeschaltet werden. 
Eine Lösung ist in Sicht und wird voraussichtlich ab "photokina
2002" eingeführt werden können. 

Die vergütete Sucherfenster erhöhen merkbar den Kontrast des
Sucherbildes in der Leica M7. Auch diese vergütete Sucherfenster 
werden später in Leica M6/M6 TTL-Kameras nachgerüstet werden können 
(Herbst 2002)."

Translation:
I is correct that the rangefinder (patch) flare problem is caused by the
parabolic mirror.
Under certain light conditions (110° to the light source) the rangefinder
patch can become bright white and unusable.
This problem was significantly reduced by introducing a second reflective
surface in the M7 and M6 TTL, but it was not yet possible to eliminate it
completely.
However, we are working on a solution and we are confident that it will be
introduced at the Photokina 2002.
The coated viewfinder windows of the M7 enhance the contrast of the
viewfinder image visibly. In fall 2002 it will be possible to upgrade Leica M6/M6TTL
cameras with these windows.

I think this is really good news! :-)
Regards from Germany,
Alex



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Replies: Reply from S Dimitrov <sld@earthlink.net> (Re: [Leica] Rangefinder Whiteout Problem - The Answer from Leica)
In reply to: Message from "B. D. Colen" <bdcolen@earthlink.net> (RE: Tim Atherton and his on-list insults - was RE: [Leica] M3 and airport security)