Anti-Newton Glass and Huge Enlargements

[Old-N-Feeble]

I realize AN glass has little effect on relatively small prints but what about HUGE prints? Does that fine granularity of the AN glass ever show in really big prints?

 

[Old-N-Feeble]

I guess I should be more specific: Lets assume 4x5 Omega D5 with Super Chromega II head and carrier with genuine Omega glass... full-frame enlarged to 10x.

 

[Old-N-Feeble]

It'll be awhile before I build my darkroom. I'm accumulating equipment, parts and materials right now. I'm just trying to assure I acquire the right things.

 

[tedr1]

This is how understand things. I have anti-Newton glass in the carrier for my LPL, only the upper glass surface is diffuse to prevent the formation of "rings" when the glossy back of the film meets the glass. Polished glass on the lower surface of the upper glass would create Newtons Rings so the surface is diffused (by sand blasting) to prevent that.

Below the negative the lower glass is polished on both upper and lower faces, no anti-Newton treatment. The upper face of the lower glass is in contact with the underside of the negative. Unlike the back of the negative this is not a glossy polished surface, the emulsion surface is diffuse and does not form Newtons Rings. This means that when the emulsion image is projected through the lower glass there is no diffusion of the emulsion image by the AN glass because the diffused surface of the AN glass is ABOVE the negative, the glass surfaces below the negative are polished and introduce no diffusion.

I think this is right, it is a logical explanation for the AN glass being used only above the negative.

 

[Ron789]

I guess I should be more specific: Lets assume 4x5 Omega D5 with Super Chromega II head and carrier with genuine Omega glass... full-frame enlarged to 10x.

Enlarged 10x is no problem at all; I would't call that a huge enlargement. Maybe a 20x or 30x enlargement might become an issue but I even doubt that. 35mm negatives are often 15x or even 20x enlarged and I've never seen any issue due to the structure of the AN glass (that is then also 15-20x enlarged).

 

[Sal Santamaura]

...I have anti-Newton glass in the carrier for my LPL, only the upper glass surface is diffuse to prevent the formation of "rings" when the glossy back of the film meets the glass. Polished glass on the lower surface of the upper glass would create Newtons Rings so the surface is diffused (by sand blasting) to prevent that...

Both surfaces of 4x5 LPL upper glass are textured. I can't be absolutely certain, but the texture appears to have been molded in, not achieved by sandblasting. Note that, if one enlarges Kodak 320TXP film, there's no need for a textured upper glass, as Newton's rings won't form because of the film base's retouching coating.

...Below the negative the lower glass is polished on both upper and lower faces, no anti-Newton treatment...

LPL lower glazing is float glass. Both of its surfaces are inherently smooth; no polishing is necessary.

...Unlike the back of the negative this is not a glossy polished surface, the emulsion surface is diffuse and does not form Newtons Rings...

Again, this is dependent upon the particular film negative. Both Fuji Acros and Kodak 100TMAX (TMAX 100, or TMX) have sufficiently glossy emulsion surfaces to form rings under many environmental conditions.

 

[Hilo]

I find this a very good question, but not for the reason of what you imply, that the granularity would show on a (large size) print. I simply have never seen that, nor have I heard anything about it.

However, AN glass does influence image in my opinion. This is a personal experience based on working with Leitz Focomat Ic, IIc and Valoy II enlargers. What I am trying to say is that it may be all different with another enlarger, I don't mean to conclude my experience is a fixed parameter!

I print a lot of 50X60cm on fiber (20X24). I don't know if you see that as a large print, or huge. I have 135mm negatives and 120 as well, up to 6X9.

In general I find the use of AN glass influences something to do with contrast. When I do a print using AN glass and it is slightly too soft, but not enough to go to the next harder filter - then I remove the AN glass and almost always the contrast will be perfect. The other way around it is the same. I like it a lot, because it gives me another tool for very fine adjustments. For the Focomat IIc I have negative holders with AN glass and negative holders with glassless inserts. It took me awhile to find the right solutions.

For the Ic it is quite simple: I take away the AN glass that slides over the condenser that presses flat the negative. And I fabricated from thin pvc sheet something that prevents the negative touching the glass of the condenser. This solution also works with the Valoy II in combination with switching between AN treated condenser and clear condenser.

Let's say I prefer to print without glass in the holder, for obvious reasons (less dust). But many times I go to negative holders with AN glass. Everything is subjective, because already between the three Leitz enlargers I get different prints, in terms of contrast and even illumination. The trick is to remember and make it work for you.

 

[EdSawyer]

The texture would have to be in focus for it to be an issue, right? I'd be surprised if the depth of focus would allow that in most enlarging situations.

 

[RobC]

I noticed AN glass grain showing in 20x16 print from my L1200 using Durst AN Glass. Someone advised me that the DeVere AN glass is much better and you can order it from them and have it cut to whatever size you need. I haven't done it so can't vouch for the accuracy of what I was told. But yes, some AN glass will show its grain/texture but only if your're looking for it. Not all AN glass is equal.

the only way you're going to know for sure is a) if you find it in print by doing side by side test with AN and without and b) if you found the AN grain in test (a) then buy some new AN glass and do same test as in (a) to see if new glass solves the problem.

speak to them and find out what it costs.

http://www.odyssey-sales.co.uk/

 

[Old-N-Feeble]

I find this a very good question, but not for the reason of what you imply, that the granularity would show on a (large size) print. I simply have never seen that, nor have I heard anything about it.

However, AN glass does influence image in my opinion. This is a personal experience based on working with Leitz Focomat Ic, IIc and Valoy II enlargers. What I am trying to say is that it may be all different with another enlarger, I don't mean to conclude my experience is a fixed parameter!

I print a lot of 50X60cm on fiber (20X24). I don't know if you see that as a large print, or huge. I have 135mm negatives and 120 as well, up to 6X9.

In general I find the use of AN glass influences something to do with contrast. When I do a print using AN glass and it is slightly too soft, but not enough to go to the next harder filter - then I remove the AN glass and almost always the contrast will be perfect. The other way around it is the same. I like it a lot, because it gives me another tool for very fine adjustments. For the Focomat IIc I have negative holders with AN glass and negative holders with glassless inserts. It took me awhile to find the right solutions.

For the Ic it is quite simple: I take away the AN glass that slides over the condenser that presses flat the negative. And I fabricated from thin pvc sheet something that prevents the negative touching the glass of the condenser. This solution also works with the Valoy II in combination with switching between AN treated condenser and clear condenser.

Let's say I prefer to print without glass in the holder, for obvious reasons (less dust). But many times I go to negative holders with AN glass. Everything is subjective, because already between the three Leitz enlargers I get different prints, in terms of contrast and even illumination. The trick is to remember and make it work for you.

RE contrast reduction: Does this appear to be similar to using uncoated lenses or is it more similar to affecting microcontrast (acutance) at more localized areas?

 

[Old-N-Feeble]

I noticed AN glass grain showing in 20x16 print from my L1200 using Durst AN Glass. Someone advised me that the DeVere AN glass is much better and you can order it from them and have it cut to whatever size you need. I haven't done it so can't vouch for the accuracy of what I was told. But yes, some AN glass will show its grain/texture but only if your're looking for it. Not all AN glass is equal.

the only way you're going to know for sure is a) if you find it in print by doing side by side test with AN and without and b) if you found the AN grain in test (a) then buy some new AN glass and do same test as in (a) to see if new glass solves the problem.

speak to them and find out what it costs.

http://www.odyssey-sales.co.uk/

I'll research the DeVere AN glass. I'd hate to think the Omega offering is inferior but all things are possible. I would indeed be looking very closely for its affect on very large prints.

 

[RobC]

I'd say the contrast reduction with AN glass is due to diffusion, especially because he is using a condensor enlarger. Any rough surface glass will diffuse light to a degree which is the exact opposite of what your're trying to achieve with a condensor. You probably wouldn't see a difference on a diffusion enlarger.

 

[Old-N-Feeble]

I wonder of the Beseler Negaflat will work in an Omega D5. Mine is in storage so I can't try it immediately. Has anyone tried it? I realize many consider the Negaflat to be inferior to glass carriers but is it really that bad?

BTW, for very large prints I'll be using f4 or f5.6 to minimize diffraction (150mm Apo lens).

 

[Old-N-Feeble]

I'd say the contrast reduction with AN glass is due to diffusion, especially because he is using a condensor enlarger. Any rough surface glass will diffuse light to a degree which is the exact opposite of what your're trying to achieve with a condensor.

I don't doubt that, but it's in such close proximity to the emulsion that it seems it would only affect microcontrast, not overall contrast. I don't know...

 

[Bob Carnie]

I guess I should be more specific: Lets assume 4x5 Omega D5 with Super Chromega II head and carrier with genuine Omega glass... full-frame enlarged to 10x.

You are talking 40 x50 inches as long as you are using proper glass carrier there will be no issue with this type of magnification.. we focus on the emulsion and if using APO enlarging lenses with a level enlarger you are good to go.

I have seen 15 ft enlargements from 8 x10 film using proper glass setup and you would never see the AN pattern.

 

[DREW WILEY]

With the dye clouds of color film, I don't have any problem with Antinewton glass on BOTH sides of the film. Of course, all my enlargers are very
critically aligned so I focus only on the emulsion itself. But in black and white printing there are a few rare instances where I want such a huge boost
in contrast using a VC paper that a hyper-performance APO enlarging lens is just too sensitive to such nuances, so Ill back off to a more ordinary Rodagon or EL Nikkor lens. I cut my teeth on large high-contrast Cibachromes, which is about as critical a test of this issue as you can imagine. I just
installed double AN glass on a couple of precision register carriers for my latest 8x10 Durst acquisition, and have no worries.

 

[RobC]

well I think it does depend on a couple of factors. Primarily the fstop you are using. As you close down your depth of field at the negative increases and can run into the glass which would bring AN grain into print. I remember you saying Bob, you never close down past point of maxumum sharpness. Maybe he's using too small an aperture. Nope I just saw he said F4 or F5.6.

4x5 film is 0.2mm thick. Or at least the sheet I just measured is.

Some numbers:
150mm lens with 6X enlargement
F5.6 depth of field at neg = 0.0590mm so +or- 0.0295mm
F11 depth of field at neg = 0.226mm so +or- 0.113 mm
F22 depth of field at neg = 0.899mm so +or- 0.449 mm

150mm lens with 10X enlargement
F5.6 depth of field at neg = 0.0685mm so +or- 0.0343 mm
F11 depth of field at neg = 0.267mm so +or- 0.123 mm
F22 depth of field at neg = 1.07mm so +or- 0.535 mm

At F22 you could quite easily run into problems of AN Glass being in focus. Much less likely at F11 and very unlikely at F5.6

So to help avoid the problem, keep aperture as wide as is practical to give sharpness.

But finer grained AN glass is less likely to be visible if it is in focus.

 

[Bob Carnie]

With the dye clouds of color film, I don't have any problem with Antinewton glass on BOTH sides of the film. Of course, all my enlargers are very
critically aligned so I focus only on the emulsion itself. But in black and white printing there are a few rare instances where I want such a huge boost
in contrast using a VC paper that a hyper-performance APO enlarging lens is just too sensitive to such nuances, so Ill back off to a more ordinary Rodagon or EL Nikkor lens. I cut my teeth on large high-contrast Cibachromes, which is about as critical a test of this issue as you can imagine. I just
installed double AN glass on a couple of precision register carriers for my latest 8x10 Durst acquisition, and have no worries.

Drew I rarely disagree but I have found AN on both sides to be problematic . I use AN on top only

 

[RobC]

but just becasue AN glass grain is not fully in focus doesn't mean it won't show as mottled/soft grain.

 

[Bob Carnie]

In my past life I worked at Jones & Morris Photo Mural and made huge murals daily. We did all the 8ft backlight duratrans for Estee Lauder and I can assure you AN was on top of neg and clear optical glass on Bottom.. We focused on the film grain and always used two stop down principle. As well the huge rooms were black as well as the magnet board that held the material was black.

the mottling of the glass was never an issue... Also we never closed down more than two stops as we were always hungry for enlarger speed.

 

[RobC]

I rekon that must be the crux of it. Providing you have not stopped down too much you ain't going to see it. Needless to say I wasn't considering that when I saw it in my prints and have no idea what Fno I was using. But there certainly are circumstances when it will appear. I have seen it with my own eyes which is proof enough for me.

 

[Nodda Duma]

For optical testing, I've used index matching fluid (a light oil) to eliminate Newton Rings between two surfaces. Is there an analogous approach for this application?

 

[Old-N-Feeble]

For optical testing, I've used index matching fluid (a light oil) to eliminate Newton Rings between two surfaces. Is there an analogous approach for this application?

I think for 'optimal quality' I'd opt for wet-mounting but that's a PITA, isn't it?

 

[Nodda Duma]

I think for 'optimal quality' I'd opt for wet-mounting but that's a PITA, isn't it?

Yes. It's all relative

 

[DREW WILEY]

This is the kind of thing I have done for years. I NEVER EVER get anything resembling mottling or visible texture due to using AN glass on both sides.
Of course, all this is predicated by using the right kind of AN glass for the given magnification, along with the incidence of the light of enlarger lens
view, etc - in other words, I've done my homework. As far as fluid mounting is concerned, that is the kind of carrier Carlwen once offered. They don't
really look all that precise to me, in the sense I'd want to try to scrounge original Carlwen components for any given enlarger. Any serious machinist
could make something better nowadays. But then you introduce the risk of neg and glass damage with all that extra mandatory cleaning. Multiply that
numerous times if various silver masks are also involved, like some of us frequently use for superior printing control. So, despite the obvious hypothetical advantage of fluid mounting, the logistical headache never appealed to me. And if there is any image degredation due to double AN surfaces, it is invisible to the naked eye, and you'd need a helluva loupe to spot it. I have trouble seeing it with a grain magnifier. And anyone who
has actually seen my big Cibachromes or Fuji Supergloss prints knows that I'm not bluffing when I intend to make an exceptionally sharp print.