Sony a580 vs Sony a6100: read noise comparison

The Sony a580 (DSLR-A580) was measured at 8 ISO settings from ISO 100 to ISO 12800. Values were derived by Bill Claff from DxOMark lab data.

At base ISO (100) read noise is 0.55 DN. From ISO 800 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise.

The Sony a6100 (ILCE-6100) was measured at 28 ISO settings from ISO 100 to ISO 51200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 1.39 DN, or 3.3 electrons at the sensor. A second gain (dual gain) kicks in at ISO 400, cutting input-referred read noise by about 1.2 stop. From ISO 500 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 5000 don't change analog gain (digital push). Full well at base ISO is about 37,406 electrons; unity gain is around ISO 240.