M9 EXIF Data

[jagsiva]

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The aperture value shown on my M9 files appear to be inaccurate. I have looked at DNG files in both C1 Pro and LR 3.2.

 

This appears on different lenses as well, and all my lenses are coded. The exposures are fine. Has anyone seen this type of thing before?

 

Also, I am assuming there is no way to tell Aperture value in the camera itself during image playback. Shutter speed and ISO are displayed, but not ISO.

 

Thanks again for your help.

 

Jag

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[jagsiva]

I also understand that due to the lack of electronic connections between camera and lens, the M9 estimates aperture for EXIF. However, mine are off quite a bit, for example F8 shows up as F4.

[scott kirkpatrick]

You are seeing the guesstimated aperture in LR or Capture One or other tools that read the EXIF and MakerNotes information from a DNG file. This is obtained by comparing the light level seen by the "blue dot" on the front of the camera with the level seen reflected off the silver or white stripe on the front of the closed shutter inside the camera. When the angle of view that the blue dot sees is significantly different from what the lens sees, this can't be very accurate, but it works well for most evenly illuminated scenes. If you want to prove this, take a picture with a finger blocking the blue dot. The estimated aperture will be the widest that the lens is capable of, infomation that the camera gets from a table in the firmware. Producing the estimated aperture in f-stops requires a short calculation, and not all software tools do this the same way, so results may vary.

 

scott

[jagsiva]

You are seeing the guesstimated aperture in LR or Capture One or other tools that read the EXIF and MakerNotes information from a DNG file. This is obtained by comparing the light level seen by the "blue dot" on the front of the camera with the level seen reflected off the silver or white stripe on the front of the closed shutter inside the camera. When the angle of view that the blue dot sees is significantly different from what the lens sees, this can't be very accurate, but it works well for most evenly illuminated scenes. If you want to prove this, take a picture with a finger blocking the blue dot. The estimated aperture will be the widest that the lens is capable of, infomation that the camera gets from a table in the firmware. Producing the estimated aperture in f-stops requires a short calculation, and not all software tools do this the same way, so results may vary.

 

scott

 

Thanks Scott, that makes a lot of sense.

 

Jag