Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" <
> > and so higher DR values mean higher ranges of the  analog
> > signal strength we get from the CCD.
> 
> No.  Typically, the input to the A/D will be +- 3 volts, for a 6V total
> swing.  Then each bit represents N millivolts.  For a 10 bit A/D, each bit
> is 0.005859375 mv.  For a 14 bit scanner, each bit is 0.0003662109375
> mv....BUT...the scale is now shifted, since the CCD is more "sensitive".
> Remember, no matter how many bits you have, 2 is always twice 1...and we are
> dealing with integer density ratio values.
> 
> > On the other hand, bit depth is the
> > number of bits that the analog to digital converter (I suppose
> > there must be
> > one somewhere) uses to map that signal.
> 
> As my arithmetic shows above...
> 
> > Given that the analog signal is
> > continuous, any number of bits we pick will be a limiting factor
> > in that it
> > will not represent all the analog values (theoretically
> > infinite),
> 
> I don't know quite what you mean here...we only measure relative values, as
> in 2 times, 3 times, 4 times....1000 times...only integer ratio values.

What he is saying is that the CCD's voltage is analog and therefore 
infinite.

Why can't, using your above example, someone make a scanner using the 
more sensitive 14bit A/D converter on the less sensitive CCD from the 
10bit scanner. (I assume you mean sensitive as in the ability of the 
CCD to judge brighter or darker tones)  This should allow more tonal 
information over the same Density Range.

-mikeH