Digital BW, The Print

Hi Nij,

> Austin,
>
> I know you've said this before, and I'm sure we may have
> discussed it before
> (if so, I forgot!) but do you have examples of which scanners might do it
> like this? (tonal corrections in high-bit data, then convert to low-bit
> data)

I would say any scanner *SHOULD* do this...  I know my Leafscan 45 and 35 do
this.  The requirement is that the scanner have LUTs (Look Up Tables) in the
scanner, that the data passes through...and are loaded via the scanner
application with the tonal curve data you provide via a curves interface.

Basically, you need one LUT per color, and a LUT is nothing but a memory.
For a 16 bit scanner, it would be a 16 bit in and 16 bit out memory, or 128k
bytes of memory organized in 64k (16 address bits) x 16 bits per color.

> My sense tells me that scanners should be set up something like this:
> Light source -> Film -> Sensor -> 'x'bit ADC -> Data 'tonal' adjustment ->
> Convert to output bit depth -> out to computer

Correct.  Only one thing you missed, and that is either analog setpoints.
They typically happen after tonal adjustments, as data is toned in 16 bits,
so you have to wait until after the "move" to clip the setpoints.  The
setpoints can be done at the same time as the convert to 8 bit output BTW,
and the "range" of data that has the setpoints as the outer bounds is them
"mapped" into the 8 bit space.

> There must also be some additional steps I would guess, to combine colour
> data etc for a mono scan (not in the Leaf case, I know!!!),

Correct.  I've always wanted to see this mix be programmable in the scanner
driver...

> Would that be about right on flow?

Yes.

> And if so, what would your
> estimation be
> on what Nikon might have done that could result in combing on tonal
> adjustments?

Could be just bad software, or that it uses the preview for the histogram,
and the preview really is insufficient...

Regards,

Austin