Nikon Z 6III vs Sony a7S III: read noise comparison

The Nikon Z 6III was measured at 36 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 2.30 DN, or 11.9 electrons at the sensor. A second gain (dual gain) kicks in at ISO 800, cutting input-referred read noise by about 2.1 stop. From ISO 5000 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 79,728 electrons; unity gain is around ISO 520.

The Sony a7S III (ILCE-7SM3) was measured at 41 ISO settings from ISO 40 to ISO 409600. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (80) read noise is 1.01 DN, or 14.4 electrons at the sensor. A second gain (dual gain) kicks in at ISO 1600, cutting input-referred read noise by about 3 stop. From ISO 4000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 102400 don't change analog gain (digital push). Full well at base ISO is about 227,834 electrons; unity gain is around ISO 1140.