Nikon Z 6II read noise vs ISO

The Nikon Z 6II was measured at 35 ISO settings from ISO 50 to ISO 204800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 1.67 DN, or 8.5 electrons at the sensor. A second gain (dual gain) kicks in at ISO 800, cutting input-referred read noise by about 1.4 stop. From ISO 16000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 25600 don't change analog gain (digital push). Full well at base ISO is about 78,155 electrons; unity gain is around ISO 510.