I S , Dec 22, 2002; 12:13 p.m.
This is not a question, but an answer to a question I've posed
before, and could not find an answer to here or on google. It
concerned a rather odd effect I was seeing when scanning images on a
nikon coolscan III. This is what it looked like:
Obviously the dark blooming to the right should not be there. That
was scanned from a negative, and a similar effect was observed in
light areas on slides.
So, taking a small risk (but being an electronic engineer myself,
and my father a mathmatician, we didn't think we could do too much
harm), we opened up the scanner to take a look. In our case, a Nikon
Coolscan III.
The obvious thing that could have been the cause of the problem was
that the main mirror was almost completely obscured in a thick layer
of dust, which would not shift when given a blast from an air
duster.
So, it came down to some delicate work with some cotton buds,
lifting the dirt from the mirror (in a very fiddly position). And,
after doing that and putting the scanner back together (very simple
in the case of the coolscan III thankfully), this was the result:
Bit of an improvement I think, both in no longer having the
blooming, and also greater detail resolved. Both images are 100%
crops from the scanner with no adjustments made, level 7 jpeg.
Patrick Hudepohl 
, Dec 22, 2002; 01:31 p.m.
What would be the effect on slide film? Or: when I scan slides with my Coolscan III, the bright parts seem to "radiate" into the darker parts to some extent; could that be caused by dirt as well? The attached image shows a quite dramatic scan, of brightly coloured flower buds against a black background.
Slide scan: bright flower buds against black background
I S , Dec 22, 2002; 01:59 p.m.
Yes! That is the same effect.
On a positive (slide), bright parts radiate into dark, whilst with negatives dark parts radiate into light. This is because what is a dark part of the image on a negative is actually the lightest part of the actual negative you're scanning.
Presumably it is caused by the light scattering off the dusty mirror, and occurs more when there's more light passing through.
Carl Smith , Dec 22, 2002; 02:12 p.m.
Also, to a certain extent the LS4 and LS4000 have sensor blooming. But I believe a major portion of the problem is dust, which obviously somehow gets further in to the Nikons than it does with Canon or Minolta scanners, as I've never experienced a scanner that had it completely caked on from Canon and Minolta.
Peter Langfelder , Dec 22, 2002; 02:23 p.m.
Thanks for the info - blooming of shadows is a bit unusual, but I have seen the same highlight blooming on pictures taken with a lens with very dusty filter. It's just flare and image degradation caused by the dust - after all that's why we keep our lenses clean :-)
I S , Dec 22, 2002; 04:09 p.m.
That's the point...shadow blooming IS highlight blooming, but appears as a shadow because it's a negative.
Steve Bingham 
, Dec 22, 2002; 05:38 p.m.
Years ago I tried to get my old LS 1000 apart to clean it. Suspecting this might be a problem. Well I couldn't get to first base!!!! Couldn't get the darn thing OPEN. And Nikon ignored my request for info - saying take it to a shop. So I gave it my wife who rarely does anything larger than 5 x 7 anyway. She thinks it's wonderful. Shhh.
Morwen Thistlethwaite 
, Dec 22, 2002; 05:55 p.m.
I've had occasion to remove recalcitrant dust from a mirror
in a film scanner, with resulting marked improvement in image
quality. But I don't think I'd do it again, and my recommendation
is not to attempt it unless you have nothing to lose, as it'd
be incredibly easy to damage or mutilate the delicate reflective surface.
Much better to keep the scanner in an airtight plastic bag when
not in use.
Laurie Young , Dec 22, 2002; 07:41 p.m.
I've noticed similar effects, mostly the loss of detail resolved, and have long suspected that the problem might be dust inside the scanner. The question is, what to do about it? I have the collscan III and while i'm sure I could, i'm relctant to take it to pieces, as I can't afford to replace it if something goes wrong. So what is the best solution to the situation?
I S , Dec 22, 2002; 08:40 p.m.
The obvious solution is to have nikon service and clean the scanner (if they offer this service), but I'm sure they'll charge you more than a few bob to do so.
Otherwise, I'm sure someone will soon recognise this problem, and set up a business in cleaning scanners.
Or, as I'm in the UK, and a poor, starving student, I might undertake the service for a small consideration (and big disclaimer).
