Canon EOS 1000D read noise vs ISO

The Canon EOS 1000D was measured at 5 ISO settings from ISO 100 to ISO 1600. Values are Bill Claff's (Photons to Photos) direct measurements from raw files.

At base ISO (100) read noise is 1.99 DN, or 18.8 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 36,489 electrons; unity gain is around ISO 950.