AN (Anti-Newton) glass question

The Focomat IIa uses AN glass for the top glass, and plain for the lower.

Is this a universal principle? IOW, can I presume the same for any two-glass
carrier?

In article , jjs wrote:

The Focomat IIa uses AN glass for the top glass, and plain for the lower.

Is this a universal principle? IOW, can I presume the same for any two-glass
carrier?

The Matte surface of the AN glass has to be above the negative.

--
Reality is a picture perfected and never looking back.

jjs wrote in message ...
The Focomat IIa uses AN glass for the top glass, and plain for the lower.

Is this a universal principle? IOW, can I presume the same for any
two-glass carrier?



What I have heard is that the Anit-Newton glass is against the smooth base
side of the negative, and you can use plain glass against the rougher
emulsion side of the negative. I don't know if this is a fact or not; I use
glassless neg carriers.

On Mar 16, 5:09*pm, jjs wrote:
The Focomat IIa uses AN glass for the top glass, and plain for the lower.

Is this a universal principle? IOW, can I presume the same for any two-glass
carrier?

Yes, as long as it is an anti-newton negative carrier. Plain glass
carriers will have plain glass on both sides. This would be the time
you would get the "newton rings" on your print around the highlights.
Right?


Draco

On 3/19/2008 12:54 PM Draco spake thus:

On Mar 16, 5:09 pm, jjs wrote:

The Focomat IIa uses AN glass for the top glass, and plain for the lower.

Is this a universal principle? IOW, can I presume the same for any two-glass
carrier?

Yes, as long as it is an anti-newton negative carrier.

Your reply is a tautology. If the carrier has anti-Newton glass in it,
then it's an anti-Newton negative carrier.

Plain glass carriers will have plain glass on both sides. This would
be the time you would get the "newton rings" on your print around the
highlights.

I think the OP knows this.

"Draco" wrote in message
...
On Mar 16, 5:09 pm, jjs wrote:
The Focomat IIa uses AN glass for the top glass, and plain
for the lower.

Is this a universal principle? IOW, can I presume the same
for any two-glass
carrier?

Yes, as long as it is an anti-newton negative carrier. Plain
glass
carriers will have plain glass on both sides. This would be
the time
you would get the "newton rings" on your print around the
highlights.
Right?


Draco

Newton's rings are an interference pattern where two
beams of light can interfer. The usual cause is reflection
between two reflective surfaces that are very closely
spaced. In the case of an enlarger using a glass sandwich
negative holder the two surfaces are the support side of the
film and the glass next to it. By making the glass slightly
rough the reflection is broken up and the rings are not
formed. Newton's rings can be formed on the emulsion side
too but the emulsion is usually rough enough, or the amount
of reflection from the gelatin low enough, so that rings are
not produced there.
Newton's rings appear as somewhat uneven dark and light
concentric rings all over the image. They follow
approximately any lack of flatness in the two surfaces
involved.
Newton's rings are often used to measure the degree of
conformance of two closely spaced surfaces where one of them
is transparent as when testing the figure of a lens against
a standard.
I think the effect you are referring to is halation.
This is also caused by reflection, usually in film, where
bright areas are reflected back into the emulsion by the
support. All modern film has either a light absorptive
coating on the back or in a layer under the emulsion (the
usual method for color film) to eliminate halation. Halation
was a very serious problem with early glass plates where it
formed quite noticeable halows around bright objects and
reduced the contrast of more extended bright objects. Glass
plates were also coated with anti-reflective layers on the
back. It is usual for the anti-halation layer to be removed
mechanically (as in the Remjet used for Kodachrome and some
motion picture stocks) or for the dyes it contains to be
made colorless by the sulfite in the developer or fixing
bath.


--
---
Richard Knoppow
Los Angeles, CA, USA

Yes, as long as it is an anti-newton negative carrier.

I'm glad that was brought up. Quite frankly, I just presumed the negative
carrier in question would need anti-newton glass. I will describe it and
perhaps someone can enlighten me. The glass is for the Saltzman 8x10
enlarger. The carrier works with two plates of glass (exactly 8x10") to
sandwich the negative. There is nothing whatsoever to separate the glasses,
except the negative. One removes the lower glass, does what he can to remove
dust, replaces the glass, and swings four tension clips over the edges of
the glass.

Requires AN glass, no?

Thank you all!

In article , jjs wrote:

Yes, as long as it is an anti-newton negative carrier.

I'm glad that was brought up. Quite frankly, I just presumed the negative
carrier in question would need anti-newton glass. I will describe it and
perhaps someone can enlighten me. The glass is for the Saltzman 8x10
enlarger. The carrier works with two plates of glass (exactly 8x10") to
sandwich the negative. There is nothing whatsoever to separate the glasses,
except the negative. One removes the lower glass, does what he can to remove
dust, replaces the glass, and swings four tension clips over the edges of
the glass.

Requires AN glass, no?

Thank you all!

Ok for you, I just pulled my Omega 10x10 carrier out of the enlarger
and it has two sheets of standard optical glass but not AN. To my
knowledge AN appears with a Matte surface unlike standard optical grade
glass. It (AN) will look less than perfectly clear. Imop & Perhaps
Richard K. can corroborate AN is only needed with a Condenser housing, I
have an Omega diffused Halogen one of three known to exist.

--
Reality is a picture perfected and never looking back.

In article ,
"Richard Knoppow" wrote:

Newton's rings are an interference pattern where two
beams of light can interfer. The usual cause is reflection
between two reflective surfaces that are very closely
spaced.

Does a single original beam source that is split, connote two beams? If
so my guess is that, Propagation seems to be the correct term?

--
Reality is a picture perfected and never looking back.

jjs wrote in message
...
Yes, as long as it is an anti-newton negative carrier.

I'm glad that was brought up. Quite frankly, I just
presumed the negative carrier in question would need
anti-newton glass. I will describe it and perhaps someone
can enlighten me. The glass is for the Saltzman 8x10
enlarger. The carrier works with two plates of glass
(exactly 8x10") to sandwich the negative. There is
nothing whatsoever to separate the glasses, except the
negative. One removes the lower glass, does what he can to
remove dust, replaces the glass, and swings four tension
clips over the edges of the glass.

Requires AN glass, no?

Thank you all!

Do you get Newton's rings? If so AN glass will
eliminate them, if not then don't bother.
BTW, I suspect glass with anti-reflection coating on it
similar to a lens would accomplish the same purpose.


--
---
Richard Knoppow
Los Angeles, CA, USA