Digital BW, The Print

Hi Bill,

> In most cases,
> as I mentioned, the terminology comes from the pre-press world,

You are exactly right, and my Leafscan is the same way.  I have to "fool" it
into getting optical resolution by giving it any dimension I want, then
entering 99999999 in the resolution box, and it then sets it self to the
highest resolution it can.

> As I understand it, with Howtek (and other PMT?) scanners, "native
> resolution" is determined by the selected orifice size (is that the right
> term?).

I don't believe it's the aperture that determines the resolution, but the
motor increments.

> Where I guess I'm unclear is how intermediate resolutions are
> achieved.  I had thought that for, say, 3250 DPI, the scanner
> would actually
> scan at 4000 DPI and then interpolate down to 3250 DPI.  Are you
> saying it's
> done differently?

With CCD scanners, you are limited in native resolution by the CCD, and the
magnification.  It's pretty simple...the CCD has, say, 6000 sensors, with a
fixed "pitch" (distance between sensors).  That means, if you have a sensor
that has 6000 sensors, and is 2" wide, with a 1:1 magnification, you'll get
3000 samples per inch.

With PMT scanners, it uses a single sensing element, and is not limited by
an sensor "pitch" as CCD sensor scanners are.  The scanner rotates the drum
in the Y axis, and moves the head assembly in the X axis.  What ever the
motors ability to move is, is what the resolution of the scanner can be.

Apparently with the Howtek, you set the Q or I factor, which means the
scanner will pick the "native" motor movement increments that are closest to
your requested size/resolution...so in that case, no interpolation will be
done.  Also, interpolation is for up sizing, not downsizing.

Regards,

Austin