Re: [Leica] M7 meter

[S Dimitrov <sld@earthlink.net>]

Thanks,_that_was very helpfull. I don't know what could of gone wrong, I
only left the camera on for 5 days after running 60 rolls of film:-)
Slobodan Dimitrov


Guy Bennett wrote:
> 
> >Guy;
> >Very sluggish response wide open. Also, there seemed to be a great
> >amount of fluctuation or uncertainty. At other times all the lights
> >wanted to stay on. I have new batteries in it. ????
> >Slobodan Dimitrov
> 
> As for the sluggish response and light wanting to stay on, yes, sounds like
> you need new batteries. As for the fluctuation or uncertainty in the
> reading, that might be due to the vignetting of the lens wide open, which
> will also effect meter readings.
> 
> I'm appending a post by John Collier and a response by Henning that discuss
> the way metering can be effected when using the Noctilux wide open. I'm not
> sure if this will help, but it sure cleared up some questions I had about
> the issue.
> 
> Good luck and let us know how this gets resolved.
> 
> Guy
> 
> *
> 
> At 12:00 PM -0700 11/15/01, John Collier wrote:
> >It is not that the Noctilux and Summilux are not true f/1 or f/1.4 lenses
> >but that, under certain lighting conditions, the inherent wide-open
> >vignetting will affect the metering area and you will not get a strictly
> >geometrical shutter/aperture relationship happening. The meter is not being
> >fooled if you do not follow it, it will underexpose. I have dug up the scans
> >from the last time this came up and if someone would like them, just let me
> >know.
> >
> >John Collier
> 
> As John wrote, the apertures of the Noctilux and Summilux are truly
> f/1 and f/1.4, and if you follow the normal sequence, you will get
> correct exposure at f/1 and 1/1000 sec if you otherwise get correct
> exposure at f/2 and 1/250sec. However, this is only true at the
> center of the frame. The further you go to the edges, the more
> underexposed the shot at f/1 is relative to the shot at f/2. The
> metering in effect compensates slightly for this, because the falloff
> is strong enough to affect the total amount of light that hits the
> white spot (which is what gets metered) and thus the meter expects a
> slightly greater amount of exposure at f/1. If you check this out
> carefully, and do the exposure series at a constant light level,
> varying aperture and shutter as accurately as you can according to
> the meter, you will find that the center of the shots at f/1 is
> slightly overexposed compared with the other shots.
> 
> If you check your very fast SLR lenses, especially the normal to
> wider ones, you will find the same metering anomaly. This applies to
> full area, centerweighted and matrix metering; not spot except in
> certain cases where off-center spot metering is possible like on
> recent Canons.
> 
> If your camera does not seem to do this, the area you are trying to
> meter is maybe such that f/1.4 at whatever would actually give you a
> slightly overexposed (by 1/6 stop or less) shot, while f/1 at the
> next higher speed would then want to meter just at the lower edge of
> the meter's agreement.
> 
> In practice, this is all nothing to worry about. Just match the
> little lights as you normally do, and shoot. True, at f/1 the meter
> will ask for slight overexposure, but human tendency is to kind of
> push things at lower light levels, and this compensates a little bit
> for that, and besides, if you look at metering accuracy graphs,
> you'll see that most exposure meters are not dead on the whole way
> across the aperture range, and tend to underexpose slightly on the
> darker end, which also compensates for the effects noted.
> 
> Lastly, this whole exposure thing is not as much of a science as is
> sometimes made out (unless you are mainly shooting completely evenly
> lit brick walls) and bracketing can be useful if greater accuracy is
> required. Film can be off 1/3stop as well as processing, and these
> factors are often greater than any metering discrepancy. The best way
> to handle this is to practice with the film and processing of your
> choice, in conditions that you normally shoot, and meter accordingly.
> 
> --
>     *            Henning J. Wulff
>    /|\      Wulff Photography & Design
>   /###\   mailto:henningw@archiphoto.com
>   |[ ]|     http://www.archiphoto.com
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