Phase One IQ250 vs Phase One IQ3 80MP: read noise comparison

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.

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.