Archived posting to the Leica Users Group, 2000/05/21

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Subject: Re: [Leica] 40mm and 3.5cm Viewfinder?
From: john <>
Date: Sun, 21 May 2000 09:06:55 +0100
References: <> wrote:
> I own an M3 and have a 3.5 cm accessory viewfinder. I know that the field of
> view of most viewfinders and the M's built-in framelines covers only a
> fraction of the actual photo area - I'm contemplating the purchase of another
> 40mm Summicron (which I used on a CL years ago and loved) and was wondering
> how the 3.5 cm viewfinder would match up with the 40 Summicron. Would their
> fields-of-view be approximately the same? Thanks in advance.
> Jim
Your 35 mm finder should work just fine. Because of the physics of lens
acceptance angles, ( the acceptance angle of the lens get wider at closer
focusing distances because the lens is closer to the film) no optical finder
can be accurate at all focusing distances.  In the M leicas the frame lines
indicate an accurate field of view for a mounted slide at the closest focusing
distance. as you focus farther away the the image on the film becomes greater
than that indicated by the frame line. At infinity the image is about double
the thickness of the frame line larger than indicated in the viewfinder.
Remember that even at the closest focusing distance the frame line is not 100%
accurate for the negative, but for a cardboard slide mount. I am not sure the
accessory finders are set up the same way, but they will also only be accurate
at one focal length. 
I think you will be fine using the 35 finder with the 40 mm lens, just
remember at very close distances to leave a little space around your subject.
John Shick

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