Digital BW, The Print

Hi Bob,

> But if your scanner only scans at 10, 12, or 14 bit, you would surely be
> much better to do the scans at 16bit

I don't know what you mean.  No matter what the scanner bit depth, if it is
above 8, it returns 16 bit data...you even though you get 16 bits from the
scanner, you really only get 10/12/14 bits of VALID image data.

> in PS, even if it means
> going from 8bit
> output to 16 bit in PS, before doing them.

Well, I don't know that that will work as you think it will.  Let me think
this through  When you convert from 8 bit to 16 bit, you are just using the
top 8 bits of data, and the bottom are now all zeros.  Now there are 255
"gaps" between each of the valid image data points...and when you make the
moves, you then re-map them to new 16 bit values, so the lower 8 bits will
now be being used...BUT you have only 256 discrete values in the first
place.  When you go back to 8 bits though, you are just lopping off the
bottom 8 bits and any of the values that were re-mapped into values that the
top 8 bits are the same, will now not be distinct...so I believe this method
does not necessarily work, and can cause losing some of your 256 original
values.  Let me think more about it...unless you or someone else has a
thought on this...

> And your method depends on the
> scanner software being as good as PS in doing the tonal corrections - many
> aren't from what I read.

I can't imagine ANY scanner software NOT doing the tonal adjustments on high
bit data, but possibly some do...  Tonal adjustments are really nothing more
than a simple look-up table and a re-mapping, they really aren't complex
algorithms, so one being "better or worse" would be hard to do...what would
make one better or worse was if they did the mapping on low bit data instead
of high bit data.

> You also can't save the various stages of tonal
> correction if you do them in the scanner.

What do you mean by that?  I can save my tonal correction curves...if that's
what you mean?  The tonal corrections are only done in the preview window,
not to the actual scanned data, at least as far as you are seeing when
making the corrections.  What you "settle on" in the preview window is then
downloaded to the LUTs in the scanner (Look Up Tables) and applied to the
actual scanned data.  Typically preview is done at a much lower resolution
than the actual scan.

> In PS I can save each stage in high-bit tonal correction, in case
> I want to
> go back and change something. Vuescan allows some tonal changes to be made
> to the saved raw scan, but I still believe that most are best done in PS,
> and Bruce Fraser recommends sending images to the printer in 16bit, thus
> allowing PS to convert to the printer color space in 16bit, rather than
> 8bit.

Er, we're talking B&W here, and unless you have the Piezo Pro or what ever
it's called, you can't send 16 bit data to the printer...and if you aren't
using SOME form of quad tome printing, well, 8 bits of 16 bits isn't going
to matter...

Regards,

Austin