Yes, John, we have been over this before. However, it does not make sense to quantify beyond 1 electron = 1 ADU. At that point you have completely quantified the number of electrons that have been captured--you have the actual count and that is all you need.
I have yet to hear your refutation of that point.
I'm pretty certain I have addressed this before. Regardless, the fact is that cameras are *NOT* counting electrons, even if that is what we'd really want them to do. The discreet electrons come packaged in a bundle of analog noise caused by reading, amplifying, transporting, (possibly amplifying again,) and digitizing the electron charge. This extra read noise is *NOT* in units of electrons; it is analog until digitization.
With customized circuitry, Canon has been able to get the level of read noises at the highest ISO down to the equivalent of a few electrons (not a few discreet electrons!). They have been able to do this at the *highest* amplification used in the cameras. Nothing that Roger writes on his website addresses what may or may not happen with more and better amplification; he simply jumps to the conclusion that nothing is gained, and uses the fact that his 1Dmk2 has the same total read noise in electrons at ISO 3200 as it does at ISO 1600. That is not any real support for his conclusion, because ISO 3200 *IS* ISO 1600 on that camera. Had he used a Minolta K7, which uses real amplification at ISO 3200, he would have measured slightly less noise at ISO 3200, and if he had actually looked at the shadows, there would be slightly less line noise at 3200, and less chromatic noise in a RAW at 3200 than 1600 pushed to 3200. I'd offer the 1Dmk3's ISO 3200 as additional support for my claim, but the fact that it is 14 bit may make you feel that the goal post for unity gain has moved (despite the fact that mk3 ISO 3200 quantized to 8 bits is still far less noisy than the mk2's ISO 3200).
I'm sure I have shown you this chart before, in previous refutations of the "unity gain" limit:
That is the total read noise, and the isolated horizontal and vertical line noises.
The total read noise, the yellow line, is scaled to 10% to fit in with the others, and the vertical axis is the read noise normalized to ISO 100 for all other ISOs, as standard deviation in ADUs (which can be considered arbitrary units of electrons). The noises clearly show no sign of flatlining completely by 3200, as far as the trends up to 1600 are concerned, especially the line noises, which are far more visible than their statistical strength suggests. Horizontal line noise *is*, without a doubt, the most troublesome aspect of high-ISO shadow areas in Canon cameras.
Roger has nothing to really support his unity gain hypothesis; he is simply applying the concept of one equals one, but these ones are really apples and oranges; one is discreet integer values, and the other is discreet multiples of a single value, with variance at a finer degree. The ADC in these cameras can *NOT* count electrons. They can only get so close to counting them, and by all appearances, with Canon's technology, the more you amplify the signal, the more you can reduce the inaccuracy, which is why it is illogical to declare that something as arbitrary as the ADU unit is a meaningful limit to practical amplification. And the ADU truly *is* arbitrary when it is fine enough not to cause posterization of RAW data. Only when it is coarse enough to cause posterization does the actual absolute meaning of the ADU have any value (the ability to posterize).