Archived posting to the Leica Users Group, 1996/08/03

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Subject: Re: MR4 meters
From: "C.M. Fortunko" <>
Date: Sat, 03 Aug 1996 14:25:15 -0600


I wanted to do tests outside today to take advantage of good natural light.
Unfortunately, it rained today and I was unable to set up my experiment.
Paper gray cards and Leicas are not waterproof.

Please stay tuned. I wanted to do these tests over a wider range of light
intensity and composition..

I agree with you that a clever circuit without a transistor might work.
However, I was unable to get someone at Leica to speak with me. The service
department in New Jersey referred me to Germany.

I do not have the MR4  meter, but am working on the assumption that the
meters in the SL2 and M5 cameras have similar circuits.


At 09:54 PM 8/3/96 +0300, you wrote:
>>From: "C.M. Fortunko" <>
>>Frankly, I do not believe that any of the cameras using only a single
>>mercury cell (SL, SL2, and M5) can be regulated. This is because there is
>>not enough voltage to make a transistor work. I assume that the CL has a
>>similar meter circuit to the M5, although it was made by Minolta.
>For making the compensation work, it is enough, if there is one element
>in the circuit that is not linear. It may be a diode or a non-linear
>resistance such as a  light dependent resistor. Effectiveness of the
>compensation is achieved both with the type of components used
>and with correct design.
>There are tradeoffs to make between meter accuracy, simple design,
>power consumption, meter sensitivity, supply voltage and resistance to
>battery wear.
>I suppose the MR meter is a combination of simple components
>and clever design. I'm waiting for your test results with great interest.
>Best regards,
>Pasi Ohtonen