Archived posting to the Leica Users Group, 2002/08/29

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Subject: Re: [Leica] 13% and 23%
From: "Mark J. Rosen" <cmra.rosen@verizon.net>
Date: Thu, 29 Aug 2002 09:38:31 -0400
References: <200208291120.EAA18291@mejac.palo-alto.ca.us>

Chris,

But I wonder if even a small distance between the film plane and the white
spot plane could actually account for that difference because we're only
talking about a change in image size of 23x35 to 18x27, which doesn't seem
all that huge a difference.  Still big, but it's not the same ratio as 13 to
23% (which would be about a 75% increase in size).  It's only about a 25%
gain in image size over that distance that would be required for all the
numbers to work out.

In the end, I don't know.  But at least it seems conceivable that the Leica
folks worked out these numbers from sensible application of optics theory.
I'm just trying to follow the logic.

Mark

>Date: Thu, 29 Aug 2002 11:32:41 +0200
>From: Christer Almqvist <chris@almqvist.net>
>Subject: Re: [Leica] 13% and 23%

<snipped>

>I think you are correct in assuming that the distance between the
>film plane and the white spot makes some difference in calculating
>the area covered by the light meter. With the distance between film
>plane and white spot being very small, this can never account for a
>13% vs 23% difference.

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Replies: Reply from Henning Wulff <henningw@archiphoto.com> (Re: [Leica] 13% and 23%)