From: Tom Ferguson (tomf2468@pipeline.com)
Date: 02/01/00-09:21:24 AM Z
Moire is the effect of scanning (making digital dots) out of something that
is already made of regular (patterned) dots (another digital file or printed
page). Putting oil or plastic sheets will not help moire. If you want to
see moire, just scan any magazine page with "no filters" set on your
scanner.
Newton rings is the effect of two glossy surfaces touching / almost
touching. I'm weak on the physics of this, but oil will solve newton rings.
In this case the two surfaces are the film and scanner glass. This is
certainly what Erin is seeing, and most like what the originator of this
thread (Kathryn) is seeing.
For desktop scanners the best bet is to use one without glass (Scanmaker 5,
most "film scanners"). The problem is that most of us (including me) don't
spend that kind of money. Many scanners (including mine) have holders that
elevate the film a few mm above the glass. Unfortunately with large format
film, the center often sags just enough to get a few rings in the center of
your picture ;-(
You rarely see this problem scanning prints due to the fact that paper
(printers or photo) is rougher (less glossy) than film.
On my Umax Powerlook, I find a lot less newton rings with the emulsion down
towards the glass. I assume that this side is less smooth, and thus less
rings. In the original software I had to flip the image (as the scan was
backwards). In Umax's newest drive it is already set for me (confused the
heck out of me for the first week!).
Hope that helps.
-- Tom Ferguson http://www.pipeline.com/~tomf2468/index.html> From: Dave & Erin <dfisher@nstar.net> > > My name is Erin and I am a grad student and I scan a lot of my negs. The > moire pattern is common when scanning negatives. At school I am using a > Linotype scanner and it came with a liquid solution that you put some on the > scanner and then lay your negs down and it prevents the moire pattern.<SNIP> > >> From: Kathryn Garrison <Kathryn.Garrison@Colorado.EDU> >> >> I'm hoping someone has the answer to this, I have a negative with some kind >> of damage to it... not sure what. Although I'm not able to see it through >> the loupe or projected from my enlarger, when I scan the negative there's a >> distinctive moire' pattern. >> >> I'd like to have a scan of this negative! Does anyone have a suggestion? I >> recall that oil is sometimes used with microscopes to improve the image, >> would I be further damaging the negative if I did that? Kathryn
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