Yesterday’s experiments with the D810 dark-field noise, which showed that Nikon employs some low-pass filtering when long exposure noise reduction is turned on, made me wonder if there was any similar filtering at high ISO settings, a la the Sony a7S.
I looked at one of the green channels of exposures made at ISO 64 and ISO 50K at 1/8000 seconds, with all in-camera noise reduction turned off.
No low-pass filtering is evident.
What is you turn high ISO noise reduction on? Here is a dark-field exposure with it set to “High”:
No low-pass filtering is evident. I checked “Low” and “Normal” with the same results.
High ISO NR does do something, though. Here’s the histogram with it set to “Off”:
And set to “High”: