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Archive 2023 · Coded lens giving erratic apertures on M11

  
 
mark1958
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p.1 #1 · p.1 #1 · Coded lens giving erratic apertures on M11


I received a Leica 90mm f2.0 APO lens that was 6 bit coded at the factory.
When I have the camera set to Auto lens recognition--- it recognizes the Leica 90/2 but gives almost random aperture readings. However when I turn off auto lens recognition-- the Apertures are close... but they start at f1.7 instead of 2. Not sure why that might be.



Apr 19, 2023 at 10:29 PM
highdesertmesa
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p.1 #2 · p.1 #2 · Coded lens giving erratic apertures on M11


mark1958 wrote:
I received a Leica 90mm f2.0 APO lens that was 6 bit coded at the factory.
When I have the camera set to Auto lens recognition--- it recognizes the Leica 90/2 but gives almost random aperture readings. However when I turn off auto lens recognition-- the Apertures are close... but they start at f1.7 instead of 2. Not sure why that might be.


Leica M lenses are not electronically connected to the camera and do not transmit aperture data – the 6-bit code reader on the mount only reads the code that tells the camera what lens it is, nothing else. The aperture data in EXIF is the camera's best guess based on the image. Sometimes this is accurate, most often it's only somewhat close. Sometimes it's wildly off. Just the other day, I shot something at f/8 infinity that it reported as f/1.4



Apr 19, 2023 at 10:39 PM
Fred Miranda
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p.1 #3 · p.1 #3 · Coded lens giving erratic apertures on M11


I second @highdesertmesa's statement! When using Leica M bodies, the aperture value is merely an estimation due to the absence of electronic communication between the lens and camera.

A sensor located at the front of the camera calculates the aperture estimation.



Apr 19, 2023 at 10:45 PM
highdesertmesa
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p.1 #4 · p.1 #4 · Coded lens giving erratic apertures on M11


Fred Miranda wrote:
I second @highdesertmesa@'s statement! When using Leica M bodies, the aperture value is merely an estimation due to the absence of electronic communication between the lens and camera.

A sensor located at the front of the camera calculates the aperture estimation.


The aperture estimation in EXIF is also reported by my SL2-S with M lenses



Apr 19, 2023 at 10:51 PM
mark1958
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p.1 #5 · p.1 #5 · Coded lens giving erratic apertures on M11


Highdesertmesa and Fred.. Thanks so much. I do appreciate learning this. I wasted a lot of time trying to figure out what was wrong. Mark


Apr 19, 2023 at 11:34 PM





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