Canon EOS 50D vs Canon EOS 550D: read noise comparison

The Canon EOS 50D was measured at 7 ISO settings from ISO 200 to ISO 12800. Values were derived by Bill Claff from DxOMark lab data.

At base ISO (200) read noise is 7.94 DN. From ISO 800 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise.

The Canon EOS 550D was measured at 8 ISO settings from ISO 100 to ISO 12800. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 6.45 DN, or 11.6 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 25,726 electrons; unity gain is around ISO 180.