Phase One IQ3 80MP vs Phase One P45+: read noise comparison

The Phase One IQ3 80MP was measured at 7 ISO settings from ISO 50 to ISO 3200. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (50) read noise is 20.25 DN. A second gain (dual gain) kicks in at ISO 1600, cutting input-referred read noise by about 1.5 stop. From ISO 1600 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise.

The Phase One P45+ was measured at 5 ISO settings from ISO 64 to ISO 800. Values were derived by Bill Claff from DxOMark lab data.

At base ISO (64) read noise is 18.13 DN. From ISO 64 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise.