FujiFilm X-E1 read noise vs ISO

The FujiFilm X-E1 was measured at 16 ISO settings from ISO 200 to ISO 6400. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (200) read noise is 0.65 DN, or 5 electrons at the sensor. From ISO 800 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 2500 don't change analog gain (digital push). Full well at base ISO is about 29,453 electrons; unity gain is around ISO 1530.