Canon EOS 100D read noise vs ISO

The Canon EOS 100D was measured at 9 ISO settings from ISO 100 to ISO 25600. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 7.52 DN, or 14.5 electrons at the sensor. From ISO 3200 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 27,646 electrons; unity gain is around ISO 190.