Canon EOS 450D vs Canon EOS 500D: read noise comparison

The Canon EOS 450D was measured at 4 ISO settings from ISO 200 to ISO 1600. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (200) read noise is 9.92 DN, or 10.5 electrons at the sensor. Read noise keeps falling across the measured range, so the camera isn't fully ISO-invariant there. Full well at base ISO is about 32,620 electrons; unity gain is around ISO 210.

The Canon EOS 500D was measured at 8 ISO settings from ISO 100 to ISO 12800. Values were derived by Bill Claff from DxOMark lab data.

At base ISO (100) read noise is 7.46 DN. From ISO 1600 up the camera is effectively ISO-invariant: raising ISO further doesn't meaningfully lower shadow noise.