Raymond Daley said:
I'd like to debunk this as complete utter rubbish.
My scanner gets these streaks ONLY if I scan in colour.
I scanned a newspaper for a photo last night, the preview scan had the
streaks.
Then I switched to greyscale and they were gone.
So this dust theory just got shat on from a great height. care to suggest
something else?
its clearly something to do with the colour sensors.
Perhaps I can help.
Being one of the nice Agfa scanners that they are, means it most likely uses
a CCD Sensor consisting of an individual row of pixals each for RGB. (my
Snapscan 1236s and Studiostar certainly do)
Clearly these rows are separated by some amount and from memory was 16-32
pixals but the exact amount is irrelevant, but the fact that they are
separated is the root of problems like yours.
(When scanning in colour, the scanners software will align all three
recorded channels.)
Here is the important bit though,
The Optical path will need to provide a non-obstructed transmission of light
from the Lightsource for all three rows of the colour filtered (RGB) Sensor
or you will see strange bands of colour instead of say, the White card you
were scanning.
Common colours will be Cyan, Yellow or Magenta because it's highly likely
only one of the rows isn't getting light, thereby leaving only two Primary
colours to mix, giving us the above colours instead of White.
So therefore any misalignment of mirrors or dark specs of crap on the
mirrors or lens or even CCD surface, will give you those results.
Also, the Lightsource itself has to be aligned so that it illuminates all
three rows of the Sensor or you will get the above or worst still,
light/sensor calibration failure at start up.
The reason why you dont have a problem with B&W is simple.
It only uses one row of the Sensor and my guess is the Green channel because
(once again from memory) the green is the middle row and would recieve a
more balanced light from the Lightsource. Another thing is the middle pixal
row is more tolerant to light misalignment by either the mirrors or
Lightsource.
But the point is, you will not get any colour bands if the Light source is
obstructed in any of the above ways, because that one channel is converted
to Grayscale (B&W).
I haven't been able to read any of your earlier posts, but if its had a fall
or whatever, something could easily be out of alignment, this includes the
Sensors circuit board mounted behind the lens.
But don't forget, if some opaque gunk is stuck to a mirror and therefore
blocking light to six pixals on the Red channel, you will see a six pixal
wide Cyan band running down the scanned White card. And if (wrt) the middle
two of those six, the adjacent Green two also suffered from gunk, you would
see two Blue pixals with two Cyan each side for example.
But its probably an alignment issue.
Hope to have helped.
Mark Kelepouris
