Archived posting to the Leica Users Group, 1999/01/15

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Subject: Re: [Leica] finder brightness
From: Simon Ogilvie <sno@esi.co.uk>
Date: Fri, 15 Jan 1999 14:47:54 +0000

"Martin V. Howard" <marho@ida.liu.se> wrote:
>Guido Ridoli wrote:
>> 
>> Is it possible to measure the brightness and focal lenght of an
>> external finder for example, there is a great difference in
>> brightness between a 35mm finder SBLOO and a 35 mm WEISU;
>> and if it is, can we measure a "kind of f/stop" for an external
>> finder?
>
>Shine a light of known strength through the finder and measure the
>strength of the light (lux? lumen? something else?) on the other side.
>Would that work for an absolute rating?
>
>Illuminate the white side of a grey-card (90% reflectance) with
>uniform diffuse light.  Use a spot meter to measure through the view-
>finder to get a reading.  Use same spot meter to measure through another
>viewfinder.  Provide a relative rating.  Feasible?

This is entirely feasible and is exactly what I did to compare the
brightness of my M6 finder with that on my Mamiya 7.  I got fed up
with people denigrating the Mamiya and saying that the Leica 
viewfinder was much brighter.  I was convinced that there was very
little difference and the test proved that to be correct.  The M6
viewfinder is indeed brighter than the Mamiya but only by a small
fraction of a stop.

Simon.