Re: [Leica] Metering anomaly on M6 TTL with Noctilux

[John Collier <jbcollier@home.com>]

It is due to vignetting inherent in large aperture lenses. Check out Gunter
Osterloh's book Leica M, The Advanced School of Photography for a complete
explanation. If you do not have this book, check at your library, otherwise
I would cheerfully send you a jpeg of the relevant pages.

John Collier

> From: "Simon Lamb" <simon@sclamb.com>
> 
> I have noticed something strange with the metering on my M6 when using a
> Noctilux.  In order to explain in as few words as possble I will use the
> following symbols to show the symbols that are present in the viewfinder:  >
> o <
> 
> I was intending to take a picture at f/1 and at 1/60 second the viewfinder
> reading was  > o  (1/2 stop underexposure)
> As I was at f/1 I set the shutter speed to 1/30 second and the viewfinder
> reading was  o <  (1/2 stop overexposure, as you would expect)
> 
> I assumed that if I rotated the aperture ring to the 1/2 stop between f/1
> and f/1.4 I would get a viewfinder reading of  o  (correct exposure), but
> what I got was still  o <  (1/2 stop underexposure).
> 
> I has to set an aperture of f/1.4 before I got a viewfinder reading of  o
> (correct exposure).
> 
> It appears that instead of f/1 at 1/60 second being the same as f/1.4 at
> 1/30 second it is actually an additional 1/2 stop.  This is not in general a
> major issue as 1/2 stop in many cases is barely noticeable, but I wondered
> if anyone else had noticed this happening.  However, I was using Scala
> pushed to 400 and 800 and the 1/2 stop does make a difference.  I am using
> an M6 .85 TTL with the Noctilux.
> 
> Simon
> 
> 
>