Google Pixel 3 XL read noise vs ISO

The Google Pixel 3 XL was measured at 22 ISO settings from ISO 56 to ISO 7200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (56) read noise is 0.66 DN, or 4.8 electrons at the sensor. From ISO 250 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 800 don't change analog gain (digital push). Full well at base ISO is about 7,019 electrons; unity gain is around ISO 410.