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Sony a7II uncompressed raw dark-field histograms

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Sony posted the Release 2.0 firmware for the a7II yesterday. Among other things, the release makes uncompressed raw an option.

I did a set of dark-field histograms with no lens attached, the shutter set to 1/2000 second, and the drive mode to single shot. at all ISO settings.  I’m posting all the whole stop ones and certain others that are interesting to me.

ISO 100. All 14 bits present. Pretty tight standard deviation.
ISO 100. All 14 bits present. Pretty tight standard deviation.
ISO 200. Just about what you'd expect.
ISO 200. Just about what you’d expect.
ISO 300. Again, this is textbook.
ISO 300. Again, this is textbook.
ISO 800. Still looking normal.
ISO 800. Still looking normal, except for those empty buckets. What’s that about?
ISO 1600.
ISO 1600. Now we’re seeing a lot of depopulation.
ISO 2000.
ISO 2000.  The red channel and one of the green channels are showing a combing effect that I associate with digital processing that has gain less than one. However, the other two channels have none of the abnormally-high buckets.
ISO 2500.
ISO 2500. The effect in the upper two channels is diminishing.
ISO 3200.
ISO 3200. The doubled-up hitogram buckets are gone, but the blue and the lower green channels are not really 14 bits of precision.
ISO 3000.
ISO 4000. Like ISO 3200.
ISO 5000.
ISO 5000. Now the precision of the top two channels is about 13 bits, and that of the bottom two about 12 bits.
ISO 6400.
ISO 6400. Similar to ISO 5000.
ISO 8000.
ISO 8000. The top two channels have about 12 bits of precision, nd the bottom two about 11 bits.
ISO 12800.
ISO 12800. The top two channels are quantized at about 12 bits, and the bottom two at about 10 bits.
ISO 1600.
ISO 16000. A lot like 12800.
ISO 20000.
ISO 20000. We’ve lot a bit in the upper two channels.
ISO 25600.
ISO 25600.  Similar to ISO 20000.

This is all very interesting, especially the difference between the channels. But I don’t think any of this will affect images. It appears that there’s enough read noise to provide plenty of dither as the effective precision drops with increasing ISO.

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Unless otherwise noted, all images copyright Jim Kasson.