Sony a7 vs Sony a7 III: read noise comparison

The Sony a7 (ILCE-7) 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 1.21 DN, or 4.4 electrons at the sensor. From ISO 320 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 20000 don't change analog gain (digital push). Full well at base ISO is about 58,090 electrons; unity gain is around ISO 370.

The Sony a7 III (ILCE-7M3) 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 1.09 DN, or 6.4 electrons at the sensor. A second gain (dual gain) kicks in at ISO 640, cutting input-referred read noise by about 1.8 stop. From ISO 6400 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 93,703 electrons; unity gain is around ISO 590.