Samsung GX-20 vs Samsung NX1: read noise comparison

The Samsung GX-20 was measured at 7 ISO settings from ISO 100 to ISO 6400. Values were derived by Bill Claff from DxOMark lab data.

At base ISO (100) read noise is 2.53 DN. Read noise keeps falling across the measured range, so the camera isn't fully ISO-invariant there.

The Samsung NX1 was measured at 26 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 1.80 DN, or 3.1 electrons at the sensor. From ISO 500 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Settings above ISO 12800 don't change analog gain (digital push). Full well at base ISO is about 27,428 electrons; unity gain is around ISO 170.