Archived posting to the Leica Users Group, 1999/09/17

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Subject: Re: [Leica] Consistent underexposure problem
From: Godfrey DiGiorgi <>
Date: Fri, 17 Sep 1999 17:42:59 -0700 (PDT)

First, I'd do a little testing with a gray card and a known-reliable
incident meter to determine if the M6 meter was accurately calibrated. 
I don't expect it to be wrong, but it's always the first thing to check. I
never trust anything without some testing. If the meter is found to be
off, well, the camera's on warranty so it should be exchanged or repaired
free of charge. In the meanwhile, you can adjust the ASA setting to
compensate for the error and go take some more pictures to see if that
solves your problem.

(Another interesting exercise would be to put the camera on a tripod in a
dimly lit room, focus straight on to the wall, and have a friend with a
flashlight move the flashlight around in your viewfinder frame while you
watch the meter indicators. That will give you a sense of where the
meter's sensor is seeing things. I've done this latter exercise with
several cameras over the years, it's very instructive.)

Presuming that the M6 meter is properly calibrated, if you use the meter
reading from a too bright area you will get underexposure, too dark and
you will get overexposure. (Yes, I'm sure you know that... :) So the next
thing to do is to walk around with the incident meter and the camera. Take
a light reading with the incident meter, then try metering the scene with
the M6. If your readings differ, try to see why: the M6 meter is a central
spot, selective area meter. If you look at a scene and target it on the
equivalent of an 18% gray card to take your reading, you should get the
exact same reading as the incident light meter. Using both together would
help you visualize what constitutes 18% gray in your scenes.

That gives you the baseline for what is in the Zone System Zone V or the
center of the scale. From there, you can start to see what constitutes +1,
+2, +3, -1, -2, -3 EV differences from that centerpoint so you can
evaluate and set the correct exposure based on the meter reading, which is
dependent upon the scene and the film you are using. 

It is more complicated to express all this than to do it, so please excuse
me if it sounds somewhat confusing. 


On Sat, 18 Sep 1999, Anthony Atkielski wrote:

> I could understand random exposure errors, but what could I be doing
> that would cause _consistent underexposure_?  I'm seeing it in the
> daytime, in shadows and under overcasts, and indoors.  
> What are the likely reasons for my errors?  I assume that the meter is
> working correctly and that I'm just not accustomed to using it
> correctly.