Sony DSC-RX1R vs Sony FX3: read noise comparison

The Sony DSC-RX1R was measured at 28 ISO settings from ISO 50 to ISO 25600. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 1.12 DN, or 4.7 electrons at the sensor. From ISO 400 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 66,666 electrons; unity gain is around ISO 420.

The Sony FX3 (ILME-FX3) was measured at 41 ISO settings from ISO 40 to ISO 409600. This model has no measurement of its own; the Sony a7S III, which uses the same sensor, is shown.

At base ISO (80) read noise is 1.01 DN, or 14.4 electrons at the sensor. A second gain (dual gain) kicks in at ISO 1600, cutting input-referred read noise by about 3 stop. From ISO 4000 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 102400 don't change analog gain (digital push). Full well at base ISO is about 227,834 electrons; unity gain is around ISO 1140.