Phase One IQ180 vs Phase One IQ250: read noise comparison

The Phase One IQ180 was measured at 6 ISO settings from ISO 100 to ISO 3200. Values were derived by Bill Claff from DxOMark lab data.

At base ISO (100) read noise is 16.56 DN. From ISO 100 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise.

The Phase One IQ250 was measured at 7 ISO settings from ISO 100 to ISO 6400. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (200) read noise is 5.86 DN, or 2.5 electrons at the sensor. From ISO 3200 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise. Full well at base ISO is about 27,950 electrons; unity gain is around ISO 90.