Newton Rings on Emulsion side, how to deal?

Fatih Ayoglu · Jan 3, 2024

Hi all,

Happy New Year!

I have started to have newton rings on my Kodak P160 4x5 films when I print them sandwiched with glass carriers. I am positive the newton rings are on the emulsion side as the base side as protected with a Duratrans film as I print with unsharp masks. One way to avoid newton rings is moving to glassless carriers but that might give me less sharp prints due to film curvature.

Is there any other way to avoid NR on emulsion side?

Many thanks,
Fatih

grain elevator · Jan 3, 2024

In don't have ideas but I've had the same problem with TMX with its very smooth emulsion surface. One thing I've read was to dust with starch. I've tried and got visible spots. But maybe I didn't disperse it finely enough or it works better with large format and low magnification. If course anti-newton glass is another possibility, but I've had visible artifacts from that, too.

koraks · Jan 3, 2024

Fatih Ayoglu said:
Is there any other way to avoid NR on emulsion side?

That's what AN (Anti-Newton) glass is for. Sadly, it tends to be expensive especially in larger sizes, and there are only few sellers.
Good quality AN glass will not leave artefacts.

Fatih Ayoglu · Jan 3, 2024

koraks said:
That's what AN (Anti-Newton) glass is for. Sadly, it tends to be expensive especially in larger sizes, and there are only few sellers.
Good quality AN glass will not leave artefacts.

But also it creates lower sharpness? I can put a thin ANR glass just under the emulsion with no problem but again thinking it will lower the resolution.

Fatih Ayoglu · Jan 3, 2024

grain elevator said:
In don't have ideas but I've had the same problem with TMX with its very smooth emulsion surface. One thing I've read was to dust with starch. I've tried and got visible spots. But maybe I didn't disperse it finely enough or it works better with large format and low magnification. If course anti-newton glass is another possibility, but I've had visible artifacts from that, too.

Yes I read starch and baby powder

Ian C · Jan 3, 2024

This is the first that I’ve heard of Newton rings forming on the emulsion side of a film held in a glass carrier. I have long made temporary glass carriers or even permanent carriers for enlargers for which the maker never supplied a glass carrier. I use two sheets of window glass. To prevent Newton rings, I make a black paper mask resembling a print mat for use between the top of the negative and the upper glass to create a small gap between the glass and the negative. This small space prevents Newton rings from forming.

I’ve used the black construction paper that’s sold in art supply stores for elementary school student’s art projects. It’s generally about 0.004” (0.12 mm). This is too thin a gap to spoil the focus in enlarging or the scanning of a film. So, in the case cited in post #1, you might try this with a mat-type spacer between the lower glass and the bottom of the negative. It won’t hurt to try. I hope that this helps.

Fatih Ayoglu · Jan 3, 2024

Ian C said:
This is the first that I’ve heard of Newton rings forming on the emulsion side of a film held in a glass carrier. I have long made temporary glass carriers or even permanent carriers for enlargers for which the maker never supplied a glass carrier. I use two sheets of window glass. To prevent Newton rings, I make a black paper mask resembling a print mat for use between the top of the negative and the upper glass to create a small gap between the glass and the negative. This small space prevents Newton rings from forming.

I’ve used the black construction paper that’s sold in art supply stores for elementary school student’s art projects. It’s generally about 0.004” (0.12 mm). This is too thin a gap to spoil the focus in enlarging or the scanning of a film. So, in the case cited in post #1, you might try this with a mat-type spacer between the lower glass and the bottom of the negative. It won’t hurt to try. I hope that this helps.

I have 3M litho tape, which is 0.02mm thick, will try that one, thank you

grain elevator · Jan 3, 2024

If the glass doesn't touch the film, doesn't that mean you could just as well do without the glass? Less dust that way.

Fatih Ayoglu · Jan 3, 2024

grain elevator said:
If the glass doesn't touch the film, doesn't that mean you could just as well do without the glass? Less dust that way.

Because I print with unsharp mask, I have built a custom glass negative holder with pins to hold the mask and negative

grain elevator · Jan 3, 2024

Fatih Ayoglu said:
Because I print with unsharp mask, I have built a custom glass negative holder with pins to hold the mask and negative

Understood. My post you last replied to was meant as a response to Ian's suggestion of shimming the glass away from the film. Should have quoted it, sorry.
Anyhow if it's the emulsion side, which is usually facing down, this suggesting won't help. I suppose anti-newton glass is your best bet if you must use this film. Less smooth film might work though? Most films tend to produce newton rings only from the backing side.
Oh, another idea might be wet-mounting! I'm sure it isn't easy in practice, but would eliminate newton rings.

brbo · Jan 3, 2024

Ian C said:
This is the first that I’ve heard of Newton rings forming on the emulsion side of a film held in a glass carrier.

I've seen it more than once myself (mostly with Ektar) when humidity is high.

AN glass helps of course but will also affect the image quality. With condenser enlarger I can clearly see it on the edges, it's less noticeable in the centre. If I want no compromises I fluid mount the negative to the plain glass holder.

Mark J · Jan 3, 2024

Anti-reflection coat the lower glass.
By that I mean a vacuum-deposited AR coating, as per on lenses.
This is unfortunately not easy to arrange, or cheap, unless you are lucky to work for an optical company as I do.

This happens with Technical Pan , I had my Neg Carrier on a Meopta Magnifax coated when I used this film 25 years ago.

grain elevator · Jan 3, 2024

Mark J said:
Anti-reflection coat the lower glass.
By that I mean a vacuum-deposited AR coating, as per on lenses.
This is unfortunately not easy to arrange, or cheap, unless you are lucky to work for an optical company as I do.

This happens with Technical Pan , I had my Neg Carrier on a Meopta Magnifax coated when I used this film 25 years ago.

Would AR coated glass for framing work? A framing shop could perhaps cut glass to size for the carrier. Does AR coated glass eliminate newton rings or just reduce their visibility? For small formats, I seem to recall reading here that someone used coated glass from slide mounts.

Mark J · Jan 3, 2024

That should work, yes. The visibility of the Newton's rings depends upon the reflection value of each surface, amongst other things. If you reduce one surface reflection to 1% or 0.5% then you get a very significant reduction in the contrast of the pattern, to where it becomes invisible. Normal uncoated glass reflects about 4.5% .
I must look up the formula for Newton's ring contrast, it might even reduce more than the factor of the reduced reflection on one surface.
I have seen two types of AR coated framing glass in the past, one was probably a single coat, and had a slight yellowish tint on the print , the better one was a greenish multi-coat which was more neutral and was probably 0.5% reflect at most. Your advantage ( in cost ) is that you don't need a big piece.
The main question is probably if you can get the required thickness for your neg carrier.

koraks · Jan 3, 2024

Good AN glass will not affect sharpness of the printed image.
Maybe poorly made AN glass that's more like frosted framing glass will produce problems. I've only used high grade AN glass supplied with Durst enlargers and that doesn't degrade image quality in any way.

Using framing glass in lieu of AN glass invites images quality problems. Proceed at your own risk.

brbo · Jan 3, 2024

koraks said:
Good AN glass will not affect sharpness of the printed image.

I used ANR glass from Focal Point that I got for my scanner when they were still in business. I think it's really finely etched and I could still see deterioration on extreme edges when printing XPan frames with 80mm lens on a condenser enlarger.

The original LPL7700 ANR is far more coarse and Philips PCS150's one is even worse. Those work with no problems on diffuser heads, but not on a condenser.

Every ANR glass I ever tried with my scanner had image deterioration that I could spot when compared to wet mounted negative (plain glass - negative - mylar). If anyone knows of a source of ANR glass that is better than former Focal Point I'd really appreciate if you could point me the right direction.

koraks · Jan 4, 2024

@brbo I've never used AN glass with a scanner, so I can't comment.
Used for optical prints, I've never seen the glass cause any problems. The AN glass I have doesn't have a coarse-looking surface; its surface texture is more reminiscent of something like vaseline - it looks and feels sort of greasy (but it isn't).

This is one of those things I'm sure @DREW WILEY can comment on.

brbo · Jan 4, 2024

koraks said:
Used for optical prints, I've never seen the glass cause any problems.

As I've said, with Focal Point ANR glass I can only see a slight degradation on a condenser enlarger at the edges at the highest magnification. As far as I know I'm not the only one to learn that it's better to use diffuse illumination with ANR glass.

With naked eye, my Focal Point ANR glass look pretty much what you describe, but I can see slight roughness even with 4x magnification loupe. Yours is obviously much smoother...

koraks · Jan 4, 2024

@brbo maybe the glass I use is of better quality. Or maybe I'm not as exacting...that's very well possible, too. As said, I don't scan with AN glass and any problems with resolution would far more easily show up (at least to me) when scanning.

It's sad that AN glass is so difficult to acquire, at least affordably and in decent quality. I've got a few pieces for my Durst 138, but sadly they all problems one way or another; a scratch here or there, or even just a tiny pit...any kind of defect will show up painfully on a print.
Did you get a good deal on the Focal Point glass?

brbo · Jan 4, 2024

koraks said:
Did you get a good deal on the Focal Point glass?

In 2012 it was $38 for 261mm x 61mm (I don't have it one 261 x 61mm piece anymore, but the largest broken piece was big enough that I can still use it in my scanner and enlarger holders).

I think that was a very good price considering how much some enlarger OEM ANR costs now and how much coarser they usually are. So, yeah, I want to believe there is an ANR glass out there that is much smoother than mine, but at the same time I'm also ready to accept that those that have absolutely no effect on anything are just used with diffuse light, so I don't have to waste any more money in finding that elusive one. I know what to do if I want zero compromise.

Fatih Ayoglu · Jan 4, 2024

The lith tape has not worked, it has just shifted the NR area.
Tonight I will try with ANR glass at the bottom and glassless carrier to see if I get better results...

Mark J · Jan 4, 2024

koraks said:
Good AN glass will not affect sharpness of the printed image.
Maybe poorly made AN glass that's more like frosted framing glass will produce problems. I've only used high grade AN glass supplied with Durst enlargers and that doesn't degrade image quality in any way.

Using framing glass in lieu of AN glass invites images quality problems. Proceed at your own risk.

I wouldn't dissuade anyone from using the right type of AN glass, but I'm not sure what quality problems you envisage with good framing glass with an AR coating. Thin glass of this type is nowadays made using a float process and has excellent surface flatness, and low defects. All I would suggest is to inspect with a magnifying glass before committing to grinding a small chamfer on all the edges.

Fatih Ayoglu · Jan 4, 2024

I am also enquiring the correct dimension ANR glass from Knight Optical, there are a special company on glass work for science etc. So I am quite sure they can do a good job, (well the price for 130x150x3mm glass is GBP110 plus VAT so they better be good)

DREW WILEY · Jan 4, 2024

In the printing industry, extremely fine sifted corn starch would be applied to film with a little puff device for sake of controlling ring issues. I just don't like the idea of that getting around inside and enlarger and attracting booklice and so forth. Then scanning supply outfits sold and aerosol version of that which included a binder to keep it stuck on the film, but that kind of product was discontinued due to the nasty health consequences of the propellant. You had to carefully use it under a fume hood.

Substituting extremely flat optical glass to the emulsion side of the negative never worked for me; the climate here is simply too damp and routinely foggy to make that realistic.

The ideal "texture" of AN glass is relative to the angle of incidence as well as amount of magnification. The Focal Point and ScanTech versions work quite well with large format sheet film. But with smaller formats you ideally need a more subtle pattern like the former Durst and Omega variety, with a subtle a ripple pattern. And for 6X7 and smaller negatives, you could cannibalize the AN glass from old Gepe AN glass slide mounts and adapt them.

Nonglare framing glass is relatively useless for this application. Maybe the optically coated variety will work in a consistently dry climate. But I've tested all kinds of them and found them unsatisfactory. The coated variety has to be cut with special tooling just like tempered glass. The angle of the round glass cutter head is more acute.

brbo · Jan 4, 2024

DREW WILEY said:
The Focal Point and ScanTech versions work quite well with large format sheet film. But with smaller formats you ideally need a more subtle pattern like the former Durst and Omega variety, with a subtle a ripple pattern. And for 6X7 and smaller negatives, you could cannibalize the AN glass from old Gepe AN glass slide mounts and adapt them.

So, Durst ANR has a more subtle pattern than Focal Point ANR (I know that Gepe ANR slide mounts do not)? I need to try it then...

Newton Rings on Emulsion side, how to deal?

Fatih Ayoglu

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Newton Rings on Emulsion side, how to deal?

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