Leica M8 read noise vs ISO

The Leica M8 was measured at 5 ISO settings from ISO 160 to ISO 2500. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (160) read noise is 6.68 DN, or 10.9 electrons at the sensor. From ISO 160 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 26,800 electrons; unity gain is around ISO 260.