Sony a850 vs Sony a9: read noise comparison

The Sony a850 (DSLR-A850) was measured at 19 ISO settings from ISO 100 to ISO 6400. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (200) read noise is 1.22 DN, or 5.4 electrons at the sensor. From ISO 200 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 3200 don't change analog gain (digital push). Full well at base ISO is about 17,493 electrons; unity gain is around ISO 880.

The Sony a9 (ILCE-9) was measured at 37 ISO settings from ISO 50 to ISO 204800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 2.50 DN, or 13.7 electrons at the sensor. A second gain (dual gain) kicks in at ISO 640, cutting input-referred read noise by about 1.5 stop. From ISO 5000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 51200 don't change analog gain (digital push). Full well at base ISO is about 87,297 electrons; unity gain is around ISO 550.