Re: [Leica] Newton's rings

["Dan Post" <dpost@triad.rr.com>]

BAsically- you are right. They are the interference patterns of the
reflected light that bounces between the film and glass surface- they are or
can be so close that the light reflecting off the film, back up to the
glass, and then back down through the 'sandwich' causes the waves of this
secondary beam to react with the primary light to form the interference
pattern- the distance between rings is a multiple of the main wavelength of
the light and the varying width or the rings is from the fact that the glass
may be perfectly flat, but the film, no matter how hard it is pressed
against the glass, will never be totall flat.
One of the devices I have from a Leitz Focomat Ic is a brass ring- similar
to the regular anti-Newton ring filter, but without any glass- it only took
a moment to realize that it serves the same purpose by lifting the bottom of
the condensor, which on the FOcomat acts as the top glass of the negative
carrier a fraction of an inch- perhaps .5mm- and thus keeps the film
reasonably flat, but obviating any Newton-rings.
Dan
- ----- Original Message -----
From: "Mike Durling" <durling@widomaker.com>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Saturday, July 21, 2001 10:48 AM
Subject: Re: [Leica] Newton's rings


> I think the Newton rings are some sort of interference pattern between the
> film and glass when they are almost, but not quite, in contact with each
> other.  I think the usual fix is to install some kind of spacer, made from
> cardboard or something, to widen the gap.
>
> Mike D
>
> ----- Original Message -----
> From: "Frank Filippone" <red735i@earthlink.net>
> To: <leica-users@mejac.palo-alto.ca.us>
> Sent: Saturday, July 21, 2001 12:09 AM
> Subject: RE: [Leica] Newton's rings
>
>
> > Yes Mike your description is correct.....  I have never had them before,
> and
> > seeing these weird circular rings was a bit distressing... I thought
they
> > only happened IF you have contact .... this carrier is basiclly floating
> the
> > neg..... I think I may need to watch this, and take action if it
> > continues.....
> >
> > Frank Filippone
> > red735i@earthlink.net
> >
> >
>
>