Newton Rings!


DanPhoto@aol.com
Sun, 03 Jan 1999 12:28:40 -0500 (EST)


>Typically 35mm films have uncoated base side, while larger formats have
>gelatin on both sides in order to keep the film flat. That would account
>for the newton rings showing mainly with 35mm films.

That's true, but the surface of the gelatin is an important consideration
too. Many large format films have a retouching "tooth" on one or both
surfaces. This tooth is nothing more than a very fine texture which
provides a good surface for pencil retouching (and I'm dating myself by
declaring that in years past I did such things). This texture also
effectively reduces the formation of Newton rings by breaking up the
close marriage of surfaces in contact. Tri-X sheet film has a very
pronounced tooth; others, which the film designers deemed poor candidates
for retouching (Pan Masking Film comes to mind), have little or no tooth.

Dan



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