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Old February 24th 12, 08:50 PM posted to alt.comp.periphs.scanner
Paul
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Posts: 13,411
Default HP Scanner makes everything yellow

Mark F wrote:
On Fri, 24 Feb 2012 08:40:23 -0800 (PST), Sonnich Jensen
wrote:

Hi

Here are some pictures:
http://hot.ee/sonnich/scan1a.jpg
http://hot.ee/sonnich/scan1b.jpg

A is the original picture, 50% in order to make it fit here.
As you can see only a part of it is in the right colours.

A part of the original scan is the B - with "waves" in it, I have seen
that before and know simply to resize. But you can see the colour
difference better.

What causes the yellowness and how can I fix it?

Seems like one or more channels cut out. Also looks
intermittent.

If you repeat the scan does what looks like a good band
happen in the same place each time?

If the good band stays fixed, what happens when you
move the original on the flatbed (don't worry if some parts
are no longer scanned): does the good band stay
fixed on the flatbed or the original?

It is a HP Scanjet 2400.

WBR
Sonnich


An image for comparison to the sample.

http://antikvarhorsnaes.dk/antikvari..._Nordpolen.jpg

I don't know why, but the scanned image reminds me vaguely of the example in this article.
Like I'm looking at a CMYK representation rather than RGB. I'm no "color guy", it
just looks weird to me.

http://en.wikipedia.org/wiki/CMYK

When scanning non-solid color objects (halftones or "dots of ink"), you
get a moire pattern unless there is "descreening" turned on. The "waves"
are from interference between the sampling frequency of the scanner and
the dots in the printed cover.

http://www.scanhelp.com/288int/artco...escreentab.jpg

There is probably a problem with the image sensor on the scanner, but I'd play around
with reducing the resolution setting of the scanner, and turning on descreening. For
close work, sometimes I'd actually use a magnifying glass, to get a better idea of the
screen print frequency, so I could set the control panel for the scanner a bit better.
(To reduce Moire, maximally.)

Also, while the scanner is making the scan, monitor the white light leaking
around the edges of the scanning bed - check to see if the intensity of the
like varies as the scan is progressing. Perhaps the light source is not constant.

As another check, try scanning a 3"x5" or larger print from your
collection of film prints, as those won't have the same kind of
halftone issues. That should at least get rid of some of the
"wave" effect.

Paul