[filmscanners] Re: Avoiding Newton rings

["Anthony Atkielski" <anthony@atkielski.com>]

I think I see part of the problem:  Provia is shiny on both sides--no
visible emulsion on either side.  Apparently the emulsion side is coated.
Maybe that's why the rings turn up.  I wonder why Fuji does that.

Maybe I can try always facing the convex side of the film towards the
anti-newton glass, if it isn't already quite flat, even though this means
scanning some strips backwards.  I know that some strips look fine, but
others have a definite problem with rings.  I assume that curvature of the
film or something is getting in the way.

----- Original Message -----
From: "Arthur Entlich" <artistic-1@shaw.ca>
To: <anthony@atkielski.com>
Sent: Saturday, September 28, 2002 03:10
Subject: [filmscanners] Re: Avoiding Newton rings


The cause of Newton Rings is when a space is created between two finely
polished or glossy surfaces that is a very small space equal to or a
small multiple of white light wavelengths, which then cause interference
colors via the reflection between the surfaces. The best way to avoid
them completely is to have the space between the two surfaces be wide
enough that this phenomenon doesn't occur.

One way that this has been dealt with is by using a glass which has a
very fine etched surface which creates very small "contact points"
between the two surfaces.  Another method is to use a very fine powder
(talc is sometimes used) to again create this "airpace" with minimal
contact points.

The more often the film gets very close to the glass surface, the more
series of Newton rings will develop.  Some people use a one-sided glass
carrier to allow the film to be supported by gravity by that bottom
surface, usually having the emulsion side contact that glass surface
which has more texture and is less likely to cause Newton Rings.

If one can figure another way to create a large enough airspace, Newton
Rings can be avoided.

Art


Anthony Atkielski wrote:

> I use the glass 120 film holder on my LS-8000ED because I need to be able
to
> hold the film flat, however, I have a lot of trouble with Newton rings.
The
> weird thing, though, is that some images have multiple instances of the
> rings, and others have none.  This implies that the rings are not
inevitable
> when scanning, only common ... so there must be a way to avoid them.  What
> causes the rings on some images but not on others, and what can I do to
> avoid them when preparing and loading the film?
>
>


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