[filmscanners] RE: Avoiding Newton rings

["Laurie Solomon" <laurie@advancenet.net>]

Yes and no.  The powder is a very very fine powder and the amont used is
very sparing.  Even so, depending on the degree of enlargement, it typically
under traditional methods of enlargement acts in the same way and has a
similar appearance to that of grain or a dye cloud; in terms of scanning, I
would assume that the same would hold since the particles are very miniscule
and dispersed if used correctly.  Furthermore the glass offers some inherent
diffusion that will take the edge off any particles that do show up usually
resulting in a scan not unlike a non-condenser enlarger enlargement.

At worse, you would need to correct for the effects of the powder in
Photoshop.  Nothing is for free; everything involves a trade-off.  At least
digital spoting of particle traces be they dust or scratches is feasible in
most cases whereas the alternative Newtonian Rings are not as ameanable to
remedy digitally or otherwise once they exist.

-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Brian
Sent: Saturday, September 28, 2002 7:07 AM
To: laurie@advancenet.net
Subject: [filmscanners] Re: Avoiding Newton rings


>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.

I have read about the fine powder technique before. But wouldn't this
degrade the scanned image (kind of act like dust particles)?

Brian P.
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