F-15 Scanner Tool -

[Tim]

On Wed, 2011-08-31 at 10:09 -0400, Bob Goodwin wrote:
> 300 dpi should be fine for my needs, I believe the Brother
> HL5140 Laser can do better though.

Most recent printers can.  Mine can do 600, and it's early 1990's
vintage.

> The problem was mainly the resolution setting in xsane which initially
> defaulted to 80 dpi. The ideograph in the menu looked to me like the
> symbols for setting line width, brush size or something in Gimp and I
> did not recognize it as resolution.

I can remember having fun trying to set the resolution, years ago.  As I
recall, the setting wasn't visible, and needed some other option set
before it appeared.

Many program icons are far from obvious, even when you know what they
refer to.  Often, you remember to hit the right icon more from
remembering that it's the third one along, etc., rather than the picture
on them.  If it weren't for the pop-up tool-tips, that appear when the
mouse is hovered over something, but not clicked on, I'd have no idea
what some buttons do.

> I find the following for the HL5140 printer:    Max Resolution (
> B&W ) 2400 dpi x 600 dpi I assume 600 dpi is along the horizontal
> axis? It is presently configured to print 300 dpi.

When it comes to product specifications, I assume nothing.  But that
would seem right.

You can make some guesses with printers and scanners, based upon the
mechanics, that the horizontal resolution has some upper limit related
to the pixels it has, but the vertical resolution may be changed by
changing the moving speed of the paper or scanning sled.  Horizontal
resolution being fixed, because it doesn't move horizontally, the sled
only moves in one direction (lengthways down the page), so it can't scan
horizontally between the dots.

Just to be clear cut, <<<---- this is the horizontal direction ---->>>,
and the horizontal resolution is along it.

Though, in some cases, the higher resolution isn't actually higher
resolution, but some interpolation (software trying to guess what might
be between pixels, and faking it).  It's usually a waste of time, and
just makes huge files.  It can't create resolution that isn't there.  If
you want to artificially crispen a scan, you're probably better to do it
in some graphics software that lets you control how much it does it by.

> The HP5370C Scanner: Resolution 1200 dots per inch (dpi) optical
> resolution 1200 x 2400 dpi hardware resolution

"Hardware resolution" being "actual resolution."
> 
> unlimited interpolated resolution (HP Scanjet 5370C scanner only)

Able to fake higher resolutions than it actually does, with gay abandon.

If you believe them, that it's unlimited, then you can keep on upping
the resolution until you can see the atoms and electrons in the page.

;-)

> 
> I guess that says I should be able to set xsane to scan 600 dpi
> and produce copies

Yes, it would look like you have equipment that can run at 600 DPI, and
it's a reasonable resolution to pick for good quality document scanning
and printing.

I see little difference between 300 and 600 dpi on mine, unless I'm
printing graphics (you want the dithering dots, used to get greyscales,
rather than lithographic-only black-and-white printing, to be as tiny as
possible).  But text, on ordinary paper, looks pretty much the same.
Bearing in mind that I'm using normal typewriter sized fonts, not midget
text.

> Each time I changed resolution in xsane I had to unplug the USB
> scanner and restart xsane or things would "lock up!" Something bad was
> happening because after producing the needed copies Thunderbird Mail
> locked up too, something that is not normally a problem. I eventually
> bit the bullet and rebooted the computer.

If you can repeat the steps, and get some logs, it sounds like a bug
that should be squashed.  I have seen oddball behaviour when changing
resolutions, but I've tended to blame my scanner for screwing up more
than the computer, though I'm not sure if I blamed the right thing.

My scanner is old and knackered, but I dread trying to buy a new one,
because of all the fun and games of trying to find hardware that isn't
designed solely for use with Windows or Mac.

It could be drivers, I suppose.  e.g. If I use anything that accesses
the webcam built into my laptop, I see the "camera is on" light come on,
and it never goes off again, unless I reboot.  If the driver for your
scanner screws up, that could cause problems, and the rest of xsane,
itself, could be blameless.

-- 
[tim at localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686

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