Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Kevin 
Gulstene <kevin@d...> wrote:
> Austin-
> 
> Thanks for that.
> 
> >
> >> Why would the colour of the filter affect the relative 
intensities of
> >> the light hitting the CCD.
> >
> > Right or wrong, that doesn't have a thing to do with the 
reason.  It's 
> > the
> > property of the CCD response/artifacting to different color 
lights.  
> > Each of
> > the three lights gives different responses to the CCD and 
has different
> > artifacting.  Red, because it has the highest energy of the 
three, 
> > tends to
> > be the fuzziest, simply because of what are called bloom and 
smear.  
> > Bloom
> > is basically saturation of the sensing element, smear is 
basically 
> > crosstalk
> > between adjacent sensing elements, because of the 
intensity (this is 
> > the
> > artifact that PMT scanners do NOT suffer from, as they scan 
one "spot" 
> > at a
> > time).  Blue is the next worst, then green is the best...but not 
> > always.
> 
> I think I understand this but why is the CCD more sensitive to 
smear 
> and bloom associated with red in the absence of blue and 
green.  That 
> is, why would these artifacts appear when the light is filtered 
and not 
> appear when it goes through a ND filter?
> 
> I am interested in this because I have recently started 4x5 and 
since 
> my Umax powerlook 1100 is quite soft I'll soon be spending 
some more 
> money on another  scanner.  I'm trying to appreciate how big a 
> difference this makes in the overall scheme of things.
> 
> --
> Kevin Gulstene

I don't buy into Austin's argument.  If you scan with white light
passing thru the film and illuminating the CCD you have the
artifacts, fuzziness, blooming whatever of the entire visible
spectrum all added together.  You have the worst case.  If
there are some frequencies (color) that have a better response
you won't take advantage of it.  On the other hand if you scan
in RGB you at least have the possibility of picking which
third of the visible spectrum gives best results.  And even if
you just average the three values you ought to get better
results than just one value from a white light scan  -- like a
builtin multi-pass scan.

Kevin, as to the practical question about a 4x5 scanner, I've
used an Epson 1600 for 4x5 negs to print on an 1160 and
I can easily get as much quality out of the scan as I could
possibly get out of the printer.  Recently I purchased a bigger
printer, a 7500, and I just got an Epson 3200.  I expect them
to match very well but haven't done any definitive tests yet.

Roy
www.harrington.com