Newton's rings

[trudee yama]

I have two 4x5 negative carriers, one with glass, one without (both for the Saunders). When I get Newton rings with the glass carrier, I use the glassless carrier. Is there any other solution? Is it possible to get rid of the Newton rings and still use the glass carrier, reliably?

 

[Dave Parker]

Yup,

but you will have to purchase some "anti-Newton" glass which is not cheap..

Dave

 

[trudee yama]

ok

 

[boyooso]

You can get your ANR (anti newtwon ring) glass from Mike Sparks of Focal Point INC.

http://www.fpointinc.com/

He is reliable and nice.

You can also get "Anti Newton Ring Spray" it works, but the glass is an easier, permanent fix. I used to the the spray from Jobo.

Good Luck,

Corey

 

[eddie gunks]

a very knowledgeable friend has told me that if you put the neg emulsion side down and then use some kind of textured glass (maybe frosted i will check this) on top this will eliminate NR. the rings are caused by air being trapped, so the texture stops this. i hope it helps.

eddie

 

[Loose Gravel]

If your are using a coldlight or diffused source, change the top glass to opalized or white plexi. Then take out the white plexi under the coldlight if your exposures are too long. With white plexi in contact with the neg, you won't get rings.

Other solutions, don't use a glass carrier. I have never needed one, even with the thinner base negs. Another solution is to get one of those neg carriers that holders your neg in tension.

 

[boyooso]

In my experience you can get newton rings on either surface. I usually use ANR glass on both surfaces, and yes it is slightly textured. It is textured so that the the two surfaces of the glass and film don't get so close together and create the newton ring which is actually reflections bouncing of the two surfaces (or something like that).

I have been told that you can also use a very fine anti reflection glass. Not the frosted Anti Reflection galss. That glass has too much texture and will interfere with sharpness. If you use Anti Reflections glass you need to use the optically coated Anti Reflection glass.

Hope that helps.

Corey

 

[Ed Sukach]

"Newton's Rings" are interference bands, indicating a separation bewtween the glass plate of 1/2 wavelength of light. A possible solution might be to "shim" the plates to increase the separation between them; from ~ 0.000010" to ~ 0.001" or so. Try something like very thin strips of plastic wrap.

BTW, a variation of 0.001" in the negative's focal plane will not amount to a diddley damn.

 

[Petzi]

Normally, the Anti-Newton glass is only to be mounted as the upper glass in the neg holder, the lower glass (in contact with the emulsion) is a regular glass.

 

[Buster6X6]

Does anybody know where in Canada Anti-Newton Glass could be optained? And does it have a commercial name? Dave?
Thanks in advance

Greg

 

[Dave Parker]

Does anybody know where in Canada Anti-Newton Glass could be optained? And does it have a commercial name? Dave?
Thanks in advance

Greg

The only places I have recently seen it is Optio Sigma and Edmunds Scientific(optical), you should be able to locate either by doing a google, I don't have first hand knowledge of who might be handling it in Canada.

Dave

 

[Buster6X6]

Thanks Dave
I don't know if I will need one. For my 6X9 I have installed glass only on the bottom. For 4X5 I have glass on both sides. I have not seen any rings yet.
Mind you I have been working with 8X10 lately.For 4X5 I can always remove top glass. But it would be nice to know where to get it in case I need one.

Greg

 

[boyooso]

"Newton's Rings" are interference bands, indicating a separation bewtween the glass plate of 1/2 wavelength of light. A possible solution might be to "shim" the plates to increase the separation between them; from ~ 0.000010" to ~ 0.001" or so. Try something like very thin strips of plastic wrap.

BTW, a variation of 0.001" in the negative's focal plane will not amount to a diddley damn.

Ed,

What do you mean "interference bands"?

I can attest to the shim, I've used strips of unexposed sheet film and it can work quite well, in a pinch, sometimes.

Anyway, I'm curious what "interference bands" means.

Thanks,

corey

 

[Ed Sukach]

Light acts a wave (oversimplification... there is more, but I'll leave it out here).

When it is reflected from, or refracted through, two surfaces, two waves will be formed. When the resulting waves are in phase, it reinforces... the energy is combined; when it is reflected or refracted out of phase it cancels. What you see with "Newtons Rings" is actually caused by a very small varying thickness space; where the separation results in reflected light in phase, it is brighter; out of phase it is darker. The effect is "lines" indicating phase.
Note that the lines never cross ... that would require "in phase" and "out of phase" at the same time.

I hope that makes sense. I've done a lot of Interferometry ... and I understand the concept ... no trouble ... but explaining it in few words is tough.

 

[boyooso]

Sometimes when it is very humid, and sometimes when it is very dry I notice I have more newton ring problems, that that make any sense to you?

Corey

 

[Nacio Jan Brown]

A fairly inexpensive solution is to use "Denglass" (spelling?) for the upper glass that comes in contact with the non-emulsion side of the negative. It's a kind of non-glare glass vailable from framing stores. Be sure to pick a piece without any ripples. "Denglass" is a brand name and I'm sure the glass is available under other names.