Digital BW, The Print

I think this point is key. To the explanation of everything ;)

Austin, I haven't followed you and Todd and Mike through every twist and
turn of this discussion, but it seems like to me you are discussing the
'optimal' solution... perhaps if you were given the task of designing a
scanner from the ground up - new light source, new CCD, and on through the
system. In other words, as an engineer - you would want to match the noise
characteristics of the light / CCD 'source' to the A/D capabilities (and
probably match the quality of ALL the circuitry all the way through the
system).

However, we all know that 'marketting' and 'costing' come into these
equations. Marketing says "We just got this great new 256bit A/D chip for
$2 - let's stick that in" - where an engineer may well have noise
characteristics that demand a 11 bit A/D [is that possible] - but only have
12 or 14bit in their stock of surplus from last time.

Plus, of course, I would assume that the quality of ADC's can be extremely
variable for the same bit-depth... so more noise possibilities there too.

Best,
Nij


> -----Original Message-----
> From: Austin Franklin [mailto:darkroom@...]
<snip>
> So, the conclusion is that dynamic range and number of bits ARE DIRECTLY
> related, in that you need a minimum number of bits to represent a
> particular
> dynamic range...but just because a scanner uses a particular
> number of bits,
> that does not mean that it can actually produce a dynamic range that
> uses/requires all those bits.