Canon EOS 5D Mark IV read noise vs ISO

The Canon EOS 5D Mark IV was measured at 29 ISO settings from ISO 50 to ISO 102400. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 2.69 DN, or 11.5 electrons at the sensor. From ISO 5000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 32000 don't change analog gain (digital push). Full well at base ISO is about 67,871 electrons; unity gain is around ISO 430.