Red Streaks on scanning

[James]

I have a old Umax Astra 600s. I cleaned the glass by taking the top
off and light wiped the light bar. I can san small white like
business card but scanning large colored images I get bars of red
streak down the image right in the middle, top to bottom?

 

[CSM1]

I have a old Umax Astra 600s. I cleaned the glass by taking the top
off and light wiped the light bar. I can san small white like
business card but scanning large colored images I get bars of red
streak down the image right in the middle, top to bottom?

You probably need to clean the mirrors, lens, filter and any other parts in
the light path.
Probably have to disassemble the scanner to get to the mirrors and lens.

This site is on cleaning a Canon 8400F scanner, the Umax may have some of
the same parts.Screws are likely in different places.
http://www.carlmcmillan.com/CanonScanner/Canon.htm

 

[DenverDad]

Narrow streaks that run the length of the scan are typically the
result of dust or other contaminants at the sensor (or very near to
it). The link in the previous post sounds like a good place to
start. Do be very careful if you get to cleaning surfaces near the
actual sensor, as it is very easy to have an electro-static dischage
(ESD) event which can fry the electronics.

 

[James]

A little update, I read the cannon scanner instructions and opened the
old Umax which was similar but no cigar as Guocho would say. The
mirrors, sensor look fine and even after cleaning just the same
results streaking top to bottom in 20% of the middle?

We tried.

 

[Mark Kelepouris]

A little update, I read the cannon scanner instructions and opened the
old Umax which was similar but no cigar as Guocho would say. The
mirrors, sensor look fine and even after cleaning just the same
results streaking top to bottom in 20% of the middle?

We tried.

This sounds exactly like what I was getting years ago when I did some
serious mods to an Agfa Studiostar.
I was until I got the light and optic path properly aligned that it was OK,
so dont give up yet and see if you can detect wether something has shifted
out of alignment... did it recieve a heavy knock?

hth
Mark

 

[Raymond Daley]

Narrow streaks that run the length of the scan are typically the
result of dust

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.

 

[CSM1]

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.

The streaks show in Color because the contamination that causes the
streaks are color sensitive.

I don't know what brand of scanner you have, this page is on the Canon
Canoscan 8400F.

How to clean a Canon Canoscan 8400F
http://www.carlmcmillan.com/CanonScanner/Canon.htm

Color streaks can be caused by contamination on the optics and mirrors.

 

[Raymond Daley]

I don't know what brand of scanner you have, this page is on the Canon
Canoscan 8400F.

Agfa Snapscan E50. It works and 75% of the scan area is useable. Unless it
goes under 50% I cant ever see myself buying a new scanner or opening the
current one up to try and clean it. I gave away the last scanner (a Umax, I
forget the exact model) for the same reasons but the Agfa has negative
scanning ability (or inability if you confuse it by putting the negative
insert holder in upside that makes the scanner think its broken). If I
bought another I'd probably buy another Agfa.

 

[Mark Kelepouris]

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