Canon PowerShot G5 read noise vs ISO

The Canon PowerShot G5 was measured at 4 ISO settings from ISO 50 to ISO 400. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (50) read noise is 3.05 DN, or 6.1 electrons at the sensor. From ISO 100 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 7,951 electrons; unity gain is around ISO 100.