[Leica] Canon non-linear metering

[leicar at q.com (Aram Langhans)]

OK.  Here is a quick demonstration of what a Canon camera does with a Leica 
lens as far as metering goes.

http://gallery.leica-users.org/v/Aram/misc/meter+comparison.jpg.html

Nothing fancy, just the wall in my room.  Shot raw on my Rebel XTi with 
absolutely no post processing, so not very photogenic, but gets the point 
across.

Set camera to Aperture priority mode.  Opened lens, 50 Sumicron, to 2.0 and 
took a shot.  Meter showed as centered.  Stopped down one stop and took 
another, meter still showing as centered.  Repeated all the way to f-ll, and 
meter still shows the camera is picking an appropriate shutter speed to keep 
meter centered.  As you can see, from f-4 on, the meter is not choosing the 
correct shutter speed.  It starts to over expose and continues to do so more 
and more.  If I had gone to f-16, it would be even more overexposed.

So, the only way to get consistent results is to meter wide open in manual 
mode, then count down to the f-stop you want, and adjust the shutter the 
same number of counts, ignoring what the meter is telling you.  It will say 
you are underexposing the shot, but it will be the correct exposure when you 
see the picture.

Clear???

Aram



> From: Tim Gray <tgray at 125px.com>
> Subject: Re: [Leica] DMR or Nikon D700 and Leitax adapters
> To: Leica Users Group <lug at leica-users.org>
> Message-ID: <20101118035639.GD60960 at selenium.125px.com>
> Content-Type: text/plain; charset=us-ascii; format=flowed
>
> On Nov 17, 2010 at 10:03 PM -0500, Vick Ko wrote:
>> I'm going to have to educate myself on the "non-linear exposure issues".
>> Sounds like a PITA.
>
> Yes.  Info?  Links?
>