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Dad Photographer
The banding in the first two also curves with the radius of the sun, which to me seems that perhaps it's more of the ability of the camera to render all the tones than something technically wrong with the sensor. I would think tech problems would occur in more straight lines with the sensor matrix.
The M9 does not seem to match Velvia 50. I have been spoiled for so many years by Fujichrome 50 film. With the M9, it could be the limited capabilities to capture all tones, as you have said.