FujiFilm X-Pro3 read noise vs ISO

The FujiFilm X-Pro3 was measured at 25 ISO settings from ISO 80 to ISO 51200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (160) read noise is 1.97 DN, or 3.9 electrons at the sensor. A second gain (dual gain) kicks in at ISO 500, cutting input-referred read noise by about 1 stop. From ISO 1250 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 30,298 electrons; unity gain is around ISO 310.