Newton's Rings

[mpålsson]

Dear all,

I recently began printing with my new enlarger, a Durst L1200. My Femoneg has an Femogla-AN (anti-Newton) top panel and a Femogla (plain) bottom panel. The light source is a diffuse cold light with a milky/opaque (probably acrylic) cover. I was surprised to discover Newton's rings on all my initial prints. I printed from both Kodak TMX and Ilford Delta 100 negatives.

I've read through dozens of threads here and elsewhere regarding Newton rings. So far, I've tried:

1) wiping down the glass panels and negatives with alcohol
2) running a hair dryer over the negatives and glass
3) clamping/pinching the Femoneg

None of these tricks had any effect on preventing the Newton's rings. I feel doubly confounded because I never experienced Newton's rings with my previous set-up printing the same film stocks, in fact some of the very same negatives. That was a Beseler 45MCRX with a Beseler ANR-top/plain-bottom glass holder.

If someone has any advice to offer on preventing Newton's rings specifically with the Durst Femoneg, I'd be most appreciative to hear it.

[neil poulsen]

Try visually comparing the Fermogla top "AN" glass to the Beseler top ANR glass. What difference do you see?

This might be a long shot, but Durst USA (Hillsboro, Oregon) used to sell an "AN" glass for Durst enlargers that had more of a coating on it to prevent Newton rings, versus a true ANR glass like what you have for your Beseler.

I have some of this coated glass in a 5x7 size, and I've always been skeptical about it's ability to actually prevent Newton rings. Might it be possible to find other-brand ANR glass that would work with your Durst negative carrier?

I take the path of least resistance with my 4x5 negatives and use a glassless carrier. But if ever I do use a glass carrier, I'll probably skip the top layer and let the negative rest on the lower glass and still get some improvement over using a glassless carrier.

[Eric Woodbury]

Newton's Rings occur when the distance between two flat surfaces approach the wavelength of light ... and the light has some coherence. Therefore, you either need to disturb the flatness of the surfaces or increase the diffusion. A textured (textured relative to the wavelength of light) as the top glass neg carrier will do this. Coated glass can reduce the bouncing of light between the surfaces. There is some kind of 'micro dust' you can put on your negative before printing that separates the negative enough from the glass and doesn't show up in the print. (Never tried it.) Finally, if the diffusor is close to the negative, either making the diffusor the top glass of the negative or by placing the negative carrier within about 1/2" of the diffusion surface, the non-coherence is increased.

[Drew Wiley]

Ideally, you need real anti-Newton glass. I use it on BOTH sides of the negative. True constant flatness is absolutely necessary for my own applications. Original Durst AN glass in particular sizes is getting hard to find. And sorry, Neil, that Hillsborough source ran out of his less than ideal optically coated substitute two decades before he actually passed away. I've got all kinds of optically coated glass samples in my own experimental pile; and none of them does a sufficient job suppressing rings in this coastal climate. No problem however, even with my big custom neg carriers. I've recently used ScanTech in Los Angeles, who can cut their own excellent AN glass to any size necessary.

Both TMX and Delta are relatively slick sheet films, demanding in this respect. I work with TMax quite often.

[Oren Grad]

Both TMX and Delta are relatively slick sheet films, demanding in this respect. I work with TMax quite often.

This. TMX, especially, has a very smooth emulsion side compared to other films, so an AN top glass doesn't completely solve the problem.

[Michael R]

The emulsion side of Delta 100 shouldn’t normally form Newton rings. The TMax films and to some degree Fuji Acros can be quite problematic on the emulsion side. Certain types of optically coated glass can help under some circumstances but it can be very expensive. Above the negative, there are easier workarounds. A simple one I came up with years ago is to use a fixed out sheet of Tri-X 320. Its base is designed for retouching so it has enough “tooth” on both sides. It might also work below the negative but I never tried it. Another would be to try some of the current anti-Newton ring (etched) glasses available for scanners and in film holders used for “scanning” film with digital cameras. An example of the former is Scan-Tech’s product, which also conveniently happens to be available sized for various enlargers. An example of the latter is the glass Negative Supply is using in their film holders. Additional options are some of the better quality anti-reflection glazing/museum glasses from suppliers like Tru-Vue etc.

[Drew Wiley]

Depends what you mean by "normally", Michael. Perhaps you use dry gas heat during winter? I duuno. I use only passive electric in the darkroom, and other than Fall, and not even this Fall, this year, the climate is generally damp and foggy, so both side AN glass is essential for me year-round on all my enlargers. But yes indeed, ACROS seems even more slick than TMax. Older thicker-emulsion films did have deliberate retouching tooth on them. And just last week I did fix-out some old sheet film for potential AN usage relative to a spare registered pin glass with a plain rather than AN surface. Worth trying at least. Ordinarily I use thin frosted mylar for that purpose if needed, generally for masking or masked contact internegs etc. But I'm always fooling around with new ideas too, so what the heck.

But I found things like coated Tru-Vue glass or Denglas worthless here. There was a very unusual custom coated Zeiss glass, no doubt surplus from some unlabeled purpose long ago, which I used for awhile in my 8x10 cold light enlarger; but even that wasn't adequate with Acros sheet film, so I switched that carrier to ScanTech AN instead.

One thing which does help is developing film to the contrast level needed in advance. If you significantly boost contrast with a higher grade VC setting afterwards, then both rings and any Anti-Newton texture pattern on the glass inherently become more apparent in the print itself.

[neil poulsen]

. . . And sorry, Neil, that Hillsborough source ran out of his less than ideal optically coated substitute two decades before he actually passed away. . .

Drew, Without mentioning names, "he" was not permitted to have access to that Hillsboro glass long before he passed away. (Probably about two decades.)

. . . I've recently used ScanTech in Los Angeles, who can cut their own excellent AN glass to any size necessary. . .

This is excellent information. Thanks for including it.

It's interesting, I was told, but don't recall, the original supplier of the Hillsboro source of Durst USA glass. I do remember that the company was located in southern California. I wonder if the two are the same?

[mpålsson]

Try visually comparing the Fermogla top "AN" glass to the Beseler top ANR glass. What difference do you see?

Unfortunately, I sold off the entire system a long time ago, so I can't compare them. But from what I recall, the Beseler ANR glass was quite a bit more noticeably textured. At first glance, the Durst Femogla-AN is nearly indistinguishable from plain glass.

Finally, if the diffusor is close to the negative, either making the diffusor the top glass of the negative or by placing the negative carrier within about 1/2" of the diffusion surface, the non-coherence is increased.

I presume by diffusor you mean the diffusion panel of the light source. The diffusion panel of my Heiland LED cold head is within 5mm of the top panel of the Femoneg. It cannot be moved. As I wrote earlier, the top panel of the Femoneg is ANR glass, and the bottom is plain glass. When I look up through the Femoneg from below while inserting it into the enlarger with the LED head on, I can see the Newton's rings very clearly. They are occurring at the interface of the plain glass and the emulsion. The problem is not with the Femogla-AN (ANR) glass panel.

Moreover, I printed hundreds of 4x5 negatives using a Beseler condenser light head with a ANR-top/plain-bottom glass negative carrier in the past. I never once experienced Newton's rings.

Ideally, you need real anti-Newton glass. I use it on BOTH sides of the negative. True constant flatness is absolutely necessary for my own applications. Original Durst AN glass in particular sizes is getting hard to find. And sorry, Neil, that Hillsborough source ran out of his less than ideal optically coated substitute two decades before he actually passed away. I've got all kinds of optically coated glass samples in my own experimental pile; and none of them does a sufficient job suppressing rings in this coastal climate. No problem however, even with my big custom neg carriers. I've recently used ScanTech in Los Angeles, who can cut their own excellent AN glass to any size necessary.

Both TMX and Delta are relatively slick sheet films, demanding in this respect. I work with TMax quite often.

Thank you. I may end up hunting for a second Femogla-AN panel. As mentioned just above, the problem evidently lies with the plain glass panel. I can see quite clearly this interface is where the Newton's rings are forming. Out of curiosity, I swapped the panels so the Femogla-AN would be on the bottom. And unsurprisingly, the Newton's rings were no longer visible while looking through the carrier from below. However, I didn't test that on a real print yet and can't be sure Newton's rings still wouldn't occur due to the plain glass being on top.

This. TMX, especially, has a very smooth emulsion side compared to other films, so an AN top glass doesn't completely solve the problem.

The emulsion side of Delta 100 shouldn’t normally form Newton rings. The TMax films and to some degree Fuji Acros can be quite problematic on the emulsion side.

In six years of printing hundreds of TMX and Delta 100 on my Beseler ANR-top/plain-bottom glass carrier (with a condenser light no less), I have never experienced Newton's rings once till now. Maybe I was just supremely lucky, but I find these reports of these film stocks being more susceptible very surprising.

Certain types of optically coated glass can help under some circumstances but it can be very expensive. Above the negative, there are easier workarounds. A simple one I came up with years ago is to use a fixed out sheet of Tri-X 320. Its base is designed for retouching so it has enough “tooth” on both sides. It might also work below the negative but I never tried it. Another would be to try some of the current anti-Newton ring (etched) glasses available for scanners and in film holders used for “scanning” film with digital cameras. An example of the former is Scan-Tech’s product, which also conveniently happens to be available sized for various enlargers. An example of the latter is the glass Negative Supply is using in their film holders. Additional options are some of the better quality anti-reflection glazing/museum glasses from suppliers like Tru-Vue etc.

Thank you! I'll try to get in touch with Scan-Tech about a replacement panel for my enlarger.

[Drew Wiley]

"Durst Pro" was trying MC Schott glass thick enough and of the right kind suitable for diamond drilling to accept registration micro-pins. Not all kinds of glass can be successfully drilled, and the special AN type Condit previously used, made in Belgium, which I have in some of in my registration gear, was discontinued even earlier. I was there in person with 'Mr. Durst USA", and saw actual samples of what he intended to use. I traded him a full set of mint 138 condensers plus a surplus working high-output colorhead in exchange for a full matched diagonal punch and frame register set of the described nature. I walked away with the punch, but he defaulted on the matching accessories (which I later had to make myself); claimed that he couldn't get the glass anymore.

I don't know if the necessary glass was simply no more available, if his credit standing with them had gone bad (possible), or if he was playing another shell game with his cash and inventory as widely rumored.

He was a superb machinist, had bought out the Condit Corp and all its supplies, and really knew his Durst stuff, but was running out of complete enlargers to sell and was apparently resorting to bait and switch sales games, taking cash deposits but never delivering actual product. No sense crying about water now long under the bridge. But coming from an equipment sales background myself, and one based on total integrity as hard policy, and reliant on long-term client confidence, it was a disappointing experience.