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

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Subject: Re: [Leica] Rangefinder Whiteout Problem - The Answer from Leica
From: Henry Ting <henryting10@yahoo.com>
Date: Sat, 9 Mar 2002 10:24:00 -0800 (PST)

Can someone explain what in non-technical terms what
"parabolic mirror" is?

- --- John Collier <jbcollier@powersurfr.com> wrote:
> All I can say is that I have had a late M4-2 camera
> with no rangefinder
> flare problems. It was exactly like my M2. I also
> have an early M4-2 that
> flares exactly like my M6TTL. Others have reported
> M4-P cameras that did not
> flare like their M6 cameras. If it was a different
> mirror shape then it
> would be consistent from a certain point in
> production.
> 
> John Collier
> 
> > From: Dr.Alexander.Kraus@gmx.de
> > 
> > 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)
> > 
> > SNIP
> >
> > It 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.
> > 
> >
> 
> --
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Replies: Reply from Dr.Alexander.Kraus@gmx.de (Re: [Leica] Rangefinder Whiteout Problem - The Answer from Leica)
Reply from Henning Wulff <henningw@archiphoto.com> (Re: [Leica] Rangefinder Whiteout Problem - The Answer from Leica)