I looked at the SNR vs ISO/DIN performance of a couple of Sony cameras.
How I made these curves is described here.
As before, the way to use these curves is to find the ISO/DIN setting beyond which the Actual (red) line drops as fast as the 1.5 decibel/octave line. Beyond that point, for a given shutter speed and f-stop, you can get just as good a SNR by increasing the Exposure control in Lightroom as you can by further increasing the ISO setting on your camera, and you’ll have more headroom to boot.
On the NEX-7, ISOs of 100 (of course), 200, and 400 are well worth using, and there are small gains to be had out to 1600 (DIN 33):
On the RX-1, the situation is similar, although the curves look different because of the inclusion of the useless-for-SNR ISO 50 point:
I’m a little surprised that the Nikon D800E seems to be such an outlier, with no SNR improvements available with ISOs over (or under) 100. I only looked at octave steps, however.