Digital BW, The Print

Bill,

I understand what you are saying. But, I believe that I am infact locking
the scanner dpi setting so the scanner is "forced" to scan at an optical
resolution.

When I asked Howtek about this issue they told me that utilizing different
apertures for scanning and micro-stepping sampling, you will get a scan at a
native resolution without interpolation. The exception would be if the final
output size exceeds the maximum scan resolution of the scanner.

So infact, if one "locks" or selects an optical scan resolution and selects
an outpuit size that keeps the final scan size below 4000 dpi the scan
should still be an optical resolution scan. In addition, I was told that if
you select a resolution that is not an optical resolution, the scanner will
normally automatically scan at the next higher optical resolution and then
downsize the file thereby avoiding upward interpolation.

When setting the resolution for a scan on a Howtek drum scanner what the
user is actually setting is the "spatial" resolution. The higher the spatial
resolution the bigger the file. Optical resolution is set by the aperture on
the scanner. Optical resolution is expressed as the number of dpi that can
be discriminated, or how fine in detail each pixel is.  The wider the
aperture, the softer the image.

So for example, my original is 4"x5". I set the Q-Factor to 1.5 with a line
screen of 205. I set the desired Output size to 20"x25". Silverfast comes
back and sets the dpi at 308 (An Optical Resolution) and a file size of
90.29mb for a 16 bit grayscale image. Should I set the line screen to 157,
the resolution is set to 236, also an optical resolution. Now conversely,
sshould I set the linescreen to 150, Silverfast sets the scanner to a dpi of
225 (which is not an optical resolution) and a file size of 47.8mb. However,
according to Howtek, the scanner will scan at 236dpi (which is an optical
resolution) and then downsize the file so that no interpolation is
performed.

Now of course I may be completely wrong. If so, I am ok with that, but this
is my understanding of how this stuff works. As far as the two scans I
posted. The 4000 dpi scan will in fact appear to be sharper bue to the fact
that the scanner is using a smaller aperture. And as Howtek states, the
smaller tha aperture the sharper the detail discriminated in each pixel,
thus the greater visual presence of grain.

On another note, one of the interesting features of Silverfast is the
automatic calculation of optimal scan resolution. When the Q-Factor is set
to 1.5, all you have to do is input the desired output line screen and the
required output size and Silverfast will automatically set the optimal scan
resolution.

Mike

----- Original Message -----
From: "Bill Morse" <willym@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Saturday, April 06, 2002 12:41 PM
Subject: Re: [Digital BW] Scanning for print size: was Re: The 7...(Yadda,
Yadda)


> Mike, first I'd like to say that I am only stating my *understanding* of
> these issues- that is, I think I'm right but I'd be happy to be shown
> otherwise.
>
> Howtek says they scan at a specific dpi and adjust the aperture and drum
> speed accordingly. That's correct, but they're not referring to the print
> DPI, rather the scan or negative dpi, correct.
>
> Actually, it's only partially correct- that is, it only applies when you
> have locked the DPI settings so that the scanner is forced to one of the
> listed optical resolutions.  If you unlock the settings, the scanner will
> output any DPI you want- however, as I noted, it will do so by rezzing up
or
> down (to be truthful, I think it rezzes down, but I'm not sure.)
>
> Bottom line, as I said before, I think you are replacing scan resolution
for
> print resolution, and in the interests of lowered grain, I think you are
> just getting less resolution and more interpolation.  I looked at the two
> scans you posted (was it to the scan list?) and while one certainly had
less
> grain, what jumped out at me was that it was just much less sharp, and had
> less detail overall.
>
> It seems a shame to go through seven stages for image perfection, and then
> throw away some of the information by not using the full capabilities of
> your scanner.
>
> As I said above, this is what I *think* is happening...
>
> Bill
>
> on 4/6/02 8:15 AM, Michael Kravit wrote:
>
> Bill,
>
> You may be right but when I called Howtek they did not indicate that that
is
> the case. They publish a list of the optical resolutions for the drum
> scanner. Basically, they use a combination of drum speed, step size, and
> aperture size to obtain these rezolutions. Sol if what I understand they
are
> doing is the PMT scans at a specific dpi ie: 308dpi and the drum speed and
> x-axis movements are adjusted for the physical size of the negative.
>
> Why else would they publish such a list?
>
> Mike
>
>
> ----- Original Message -----
> From: "Bill Morse" <willym@...>
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>; "Julian Thomas"
> <julianthomas@...>
> Sent: Friday, April 05, 2002 7:21 PM
> Subject: [Digital BW] Scanning for print size: was Re: The 7... (Yadda,
> Yadda)
>
>
> > Mike, this has come up before, and I'm still unclear how you accomplish
> both
> > the below and scan at the native resolution of the scanner.  Basically,
I
> > think you are putting the DPI of the final print above the scan quality.
> >
> > If you are scanning a 4x5  to print at ~20x24 @300 DPI, you need a file
> with
> > pixel dimensions of ~6000x7200; therefor you need to scan the 4x5 @
~1500
> > DPI.  But you can't if you are scanning w/ native resolution only!  You
> > either have to scan @ 1333 DPI or @ 2000 DPI if you want native
> resolution.
> > If you force the scanner to scan @ 1500 DPI, I believe it will actually
> scan
> > @2000 DPI and rez down from there. (I think this is actually the source
of
> > what you describe as scans with less apparent grain)
> >
> > The opposite, scanner-centric process, would be to scan at the next
higher
> > scanner setting than you think you'll need, i.e. 2000 DPI, yielding an
> > 8000x10000 pixel file, and then print to 20x24 at ~400 DPI.  There are
> many
> > grain -reducing techniques that, combined with this approach, I believe
> > result in  prints with higher definition without increased grain.
> >
> > (Are your 15 minutes up yet)  ;^)
> >
> > Bill Morse
> > PhotoProspect
> > Cambridge, MA 02139
> >
> >
> >
> > ----- Original Message -----
> > From: "Michael Kravit" <michael.kravit@...>
> > To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > Sent: Saturday, April 06, 2002 12:46 AM
> > Subject: Re: [Digital BW] The 7 Truths of Digital Printing!
> >
> >
> > > Julian,
> > >
> > > I scan to a final size of 20"x24" or so. That way 99% of what I print
> will
> > > be smaller. If I must rez up, I do so with Genuine Fractals.
> > >
> > > Mike
> > >
> > >
> > > ----- Original Message -----
> > > From: "Julian Thomas" <julianthomas@...>
> > > To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > > Sent: Friday, April 05, 2002 2:20 PM
> > > Subject: Re: [Digital BW] The 7 Truths of Digital Printing!
> > >
> > >
> > > > Mike, try it - I swear by it. It makes even my haulage neg.
printable!
> > BTW
> > > > you mention scanning at  final output dpi rather than the full
optical
> > > res.
> > > > How do you resize, or do you scan multiple copies?
> > > >
> > > > Julian
> > >
> > >
> > >
> > >
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