Samsung Galaxy S6 (IMX240) read noise vs ISO

The Samsung Galaxy S6 (IMX240) was measured at 12 ISO settings from ISO 50 to ISO 800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (50) read noise is 1.34 DN, or 6.1 electrons at the sensor. From ISO 250 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 4,650 electrons; unity gain is around ISO 230.