Nokia 9 read noise vs ISO

The Nokia 9 was measured at 17 ISO settings from ISO 100 to ISO 6400. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (200) read noise is 2.58 DN, or 3.4 electrons at the sensor. Read noise keeps falling across the measured range, so the camera isn't fully ISO-invariant there. Settings above ISO 1600 don't change analog gain (digital push). Full well at base ISO is about 21,813 electrons; unity gain is around ISO 270.