Leica M11 MONOCHROM read noise vs ISO

The Leica M11 MONOCHROM was measured at 33 ISO settings from ISO 125 to ISO 204800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (125) read noise is 1.23 DN, or 3.6 electrons at the sensor. A second gain (dual gain) kicks in at ISO 400, cutting input-referred read noise by about 1.1 stop. From ISO 2500 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 12800 don't change analog gain (digital push). Full well at base ISO is about 44,112 electrons; unity gain is around ISO 360.