I agree with Jon.


Quote Originally Posted by Jon Ruyle
I guess the component coming from the adc (if any) is greater, because that comes after amplification (I think).

I think that's correct too. The Sony A900 has on-chip ADC and the read noise is the same at almost all ISO, so compared to Canon it has an extreme range of highlight headroom in low light. For example, if you shoot them both at ISO 1600, the Canon will have less shadow noise, but the Sony has over four stops more highlight headroom. I hope some day Canon can bring its ISO 1600 noise level to all ISO settings, in which case it would blow away the Sony for dynamic range in low light.