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f 11 in exif mistake?


Marten Root

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Dear all, I took this shot yesterday with a Summilux 75 @ f1.4 but my M240 is giving me (too) often wrong f stops when I review exif data in Lightroom. I know the camera is 'guessing' and 2.0 instead of 1.4 ala but f 11 instead of 1.4...? It has been 'off' too often recently... Does anyone have a clue why this might be the case?

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If the results are satisfactory, do not worry. Without accurate signal linkage the metadata is making a calculated guess which can, occasionally, be way off. From the setting it is fairly obvious that you would be using a wide aperture for your indoor picture.

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There is a small sensor on the front of the camerea that works togther with the light meetering through the lens and the information of what lens is mounted, to make an educated guess at what the apperture on the lens is at.

 

If the light hitting the sensor is different to the what the lens sees the guess will be off...

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There is a small sensor on the front of the camerea that works togther with the light meetering through the lens and the information of what lens is mounted, to make an educated guess at what the apperture on the lens is at.

 

If the light hitting the sensor is different to the what the lens sees the guess will be off...

 

Sometimes when my fingers are covering the right side light sensor then I have got wrong aperture in EXIF.

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Nothing new there. My M8 has been giving wild EXIF Exposure data since I got the camera...to the point of amusement.

Here's a good one 1/1000, f24, ISO 160, +/- 0EV....on a not very bright day.

 

It's the Leica way you know.:rolleyes:

 

cheers Dave S :)

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Somewhere on the internet there is a site that did some tests on the M8/9 (can't remember which) that showed the accuracy of the guesswork........ if I recall it was actually pretty accurate but with a scattering of results that are way off.....

 

The camera uses the difference between the metered reading from the lens light path and the tiny sensor just above the red dot to estimate the aperture.........

 

I presume it is calibrated to work with centre weighted metering and assumes you are using a 50mm lens ........

 

The body sensor just takes an ambient light reading ...... if you are using a telephoto lens or spot/multifield metering then the calculation is going to be off ...... and a light source above or close to the camera will also cause errors .... as will fingers over or close to the sensor ..... or straps.... or one of a number of other causes of reduced incident light.

 

95% of the time it gives pretty good results .... and is better than nothing .....:rolleyes:

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