Re: Meter Callibration

[Edward Meyers <aghalide@panix.com>]

On Sun, 23 Feb 1997, Stephen Kobrin wrote:

> I would like to return to an issue discussed several months ago.  My MR-4
> meter has been cleaned and repaired and I took out the battery and set the
> zero adjustment.  When I compare it to my Sekonic L-318 to check the
> reading, I find that it is about 1/2 to 3/4 of a stop high in bright light
> (that is underexposed compared to the Sekonic), but just about dead on in
> shade.  I have no reason to doubt the accuracy of a reasonably new digital
> meter.  Is it possible that the Leica Meter is accurate at low light levels,
> but slightly off when the light is stronger?  That is, that the error is
> non-linear?  
> 
> It is a relatively simple matter to make a slight mental adjustment in
> brighter light, but I am curious about others' experience with the MR-4 and
> other similar meters.  Can I be confident that, assuming a strong battery,
> the readings will be stable over time?  Are there other factors that might
> affect the relative accuracy of the meter?
> 
> Steve
> 
> 
The Leica MR-4 meter, I believe, uses a CdS cell and the Sekonic
meter uses a more modern cell. CdS must always be used carefully in
bright light, so that it doesn't point at the sun. If this happens
it has been known to lose sensitivity for a while. This could cause
some overexposure, if not left alone to regain its sensitivity.
The modern cells used in today's meters don't have this property,
I believe. Ed Meyers