Sony a7II, a7RII high-ISO spatial filtering

In several recent posts, there were reductions in dark-field noise at high ISOs with the a7II and a7RII that I attributed to in-camera processing.

Spectral analysis of the images confirms this.

For the a7II, on both sides of the transition point:

fs is the sampling frequency. Values from dc to the Nyquist frequency are plotted for both horizontal and vertical directions. The above curve is flat with frequency, which is what you’d expect if there were no spatial filtering taking place.

Turning the ISO knob up one click results in suppression of high frequencies. That’s a low-pass filter.

For the a7RII, on both sides of the transition point:

Same idea at a different ISO setting.

The results are independent of whether or not uncompressed raw mode is used.