Archived posting to the Leica Users Group, 1998/01/21

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Subject: Re: [Leica] M6 Light Meter - another question
From: "Jacques Bilinski" <>
Date: Wed, 21 Jan 1998 18:08:27 -0800

> well, I know the light is measured from the white spot. This spot has -
> according to the M6 Manual a height of 12mm. That is exactly HALF of the
> height of the whole frame. However it is stated in the same manual, that
> area covered by the meter is TWO THIRDS of the height. So here is my
> Where do they gain these additional measuring area?
> I would understand if the mesured field in the scene would cover the same
> proportion of the whole area covered by the lens as does the white spot
> the whole curtain.
> Any suggestions?
The difference could be caused by the fact that the white dot is not at the
film plane but ahead of it. So light hitting the white dot spreads to an
area bigger that the white dot when the shutter opens. This seems to imply
that the metering area depends on focal length and f-stop.