Rod wrote:
... No makers ever seem
to give an actual measured Dmax, they just give 12/14/16bit x 3 as an
indicator of potential dynamic range.

That's the problem. Some people claim that in real life you can't get
even ten bits of real data. The rest are thermal noise. You could try to
find actual test reports from the 'net...

... How
much difference would I see in A3 prints for the 12 bit A/D compared
with the 16 bit A/D of the Scan multi pro or the 14 bit of the
Microtek Artixscan 120TF?

Depends on the picture. The bits become important, if there are gradual
colours, or if you tweak the curves too much. Smooth surfaces are made
of stripes, defined by the pixels where the least significant bit flips.

-- Lassi