Re: filmscanners: ScanWit Yellow stain

[Arthur Entlich <artistic@ampsc.com>]

Dear Jerry,

I just took a look at your attachment in Photoshop.  Of course, it is
heavily artifacted due to the downsampling and Jpegging.

The first thing I always do when I look at defects is to go into
channels and look at each channel as a separate entity.  In this case,
all the problems I am seeing are in the blue channel, but of course,
since the "stain" is yellowish, that would be expected.  I can see
considerable streaking in that area, which might either be the jpegging
or it might indicate some dirt or dust or calibration problem (or
defects) with the blue CCD.  It could also, however, be a defective
light source emphasizing the yellow end of the spectrum, which, of
course, would be picked up by the blue channel.

The first thing to do is to try to rule out that this defect is
actually on the film itself.  I would try two things to try to isolate
this.  1) put the neg into the scanner the other direction, or flipped,
so the left and right are reversed.  Since the worst of the
yellowing/darkening is on the right side currently, see if it become the
left side of the scan when you reverse the image.  If so, the problem is
likely the film itself. 2) If you can sacrifice a frame of this film
that is very overexposed, try mounting it in a slide mount at 90 degrees
and see if the problem is still in the same place (in relation to the
scanner) or not.  It might be that the processing developed the streaks
on the edges of the film and they are amplified by the overexposure.
Yet another possibility is that the scanner is running into it's limits
in dealing with the Dmax at those edges.  Between a small amount of
light falloff and possibly slightly darker film at the edges (film tends
to get developed along the edges due to the sprockets carrying a bit of
extra chemistry with them between chemical vats)  If the film was drum
developed, with a film reel, that would even make it worse, as chemistry
gets trapped in the reel), anyway, you might be hitting a threshold of
the scanner CCD or electronics which is being amplified by these factors.

Lastly, typically, repairs made during a warranty period where the
repair period caused the warranty to run out, usually carry some type of
further warranty from 90 days to 1 year.  Further, if a repair is not
effective, the warranty is considered extended until the repair is
completed plus an additional time for that repair (like 90 days).  Of
course, every country has its own legislation, and every company has its
own policies concerning these matters, but most enlightened governments,
like Holland, should have laws protecting consumers in these matters.

Art



Oostrom, Jerry wrote:

   > Hi Alan,
   >
   > I recently received my scanner back from Acer, but it still showed
the same
   > problems. Here I have an example of an overexposed negative, which
gave a
   > perfect fine grained print, but scanning with the Scanwit 2720S is
useless
   > for such overexposed negatives as the negative is too dark for the (my)
   > scanwit to scan. I don't know if it is the lightbulb which gives uneven
   > illumination or dust on the lenses, CCD failures etc, but the outer
sides of
   > the CCD give too much noise on a dark negative / positive and in case
of a
   > negative this results in yellowish banding.
   >
   > Here I show you the scan, downsampled a lot of times. I did use either
   > Vuescan or Miraphoto white balance (which clearly failed, but I know I
   > checked both programs for their results: you get this strange color
cast). I
   > didn't try to remove the color cast, but you can still clearly see the
   > yellow / brownish banding along the long edges. The one on the side
of the
   > frame where the left door is located is very prominent, it
corresponds to
   > the floor side of the film holder as you insert it in the scanner.
   >
   > I sent AcerCM some of my new scans (or links to the scans) made 
with the
   > 'repaired' unit and they went very silent :-(
   > I don't know if that has to do with vacations or whatever. I think
they know
   > they didn't solve the problem during the repairs and they can't 
solve it
   > without changing a lightbulb or CCD, which is probably too expensive.
   > Unfortunately, my warranty expired during the repair period, so there
is not
   > much left to do.
   > I tried some things on my side as well to see if the problem has to
do with
   > electronic interference (somebody on this list suggested that some time
   > ago), but I don't know enough about electronics to do some educated
tests: I
   > wrapped the SCSI cable in aluminium foil, but it was to no avail.
I'll try
   > one last thing this week: hook up the scanner on another group than
the PC.
   > This is my last hope. I've seen the monitor flickering, so it could
be that
   > the current or voltage is not stable enough in the group of the PC.
   >
   > almost scanwitless,
   >