Sony a58 vs Sony a580: read noise comparison

The Sony a58 (SLT-A58) was measured at 9 ISO settings from ISO 100 to ISO 16000. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 2.77 DN, or 5 electrons at the sensor. From ISO 400 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 6400 don't change analog gain (digital push). Full well at base ISO is about 28,682 electrons; unity gain is around ISO 180.

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.