The AGC response of a Canon DSLR camera. This is for the EOS 550D, but the same system is used in all of them.

The Stimulus

This is a 440Hz tone. It starts at high level, and has dips to -6, -10, -15 and -20dB as it proceeds.

The output from the recording on the camera is:

The AGC adjusts in steps, not smoothly, so it will be impossible to cancel fully. It is also rather slow at picking up peaks, hence the overload spikes,