Right, as I said above this work shows we've nonlinear effects at work, whilst this was obvious in the past we should have taken more notice of the fact. Whilst Riemann provides say an ideal mathematical model (the ideal case) as we obserce Nature doesn't always comply, it insists on adding 'distortions' of its own.

For the same reason these 'transfer' curves have nonlinear characteristics it seems other significant interactions are at work, namely cross-coupling between color channels. We see this in color film emulsions where color bleeds from one layer to another and this effect is also nonlinear (if the bleed were linear across the transfer curve then we could simply bias it out but it's not thus in practice it's nigh on impossible to correct).

In effect this cross-coupling is essentially equivalent to cross-modulation distortion in electronic circuits and the mixing can be modeled mathematically in a similar way.

No doubt it remains to be seen whether this new work has any significant bearing on this or not.