Printing the AN pattern

[Cor]

For some time now I had the idea I could faintly discern a wavy pattern in my prints, not always but on evenly grey areas and with certain films.

First my set-up

Durst L1200 Laborator.
Condensor head.
Photocrescenta 150 watt Tungsten bulb.
Ilford multigrade filters in drawer between lamp and condensors.
Negative holder with only Anti Newton glass (from Durst) on top, no glass below for formats upto 6*6, larger with normal clear glass at the bottom.

Film HP5+ 120 format

As I said I sometimes noticed a wavy pattern which could be caused by the AN wavy pattern, so the obvious thing to do was print the same negative (a portrait with smooth mid gray tones)with AN glass and normal clear glass (both original Durst glass)

And quite clearly, side by side comparison showed that the wavy pattern was caused by the AN glass!
It's not a major difference, but side by side it is clear.

Is this a known phenomena ?

Is there a way around? I switched to AN glass because Newton rings are quite ugly. They were not frequent, humidity is mostly in the 60-80% range in my darkroom.

Best,

Cor

[mbuonocore]

I've been using anti reflection glass the past 6 months instead of anti newton glass, and I have not seen any newton rings yet. I have printed a variety of film sizes and a large variety of film stock.

I got the AN glass from focal point.

[Cor]

Interesting, but why did you switch from AN glass to anti-reflection glass (I assume that its clear, flat glass with a coating?)

best,

Cor


I've been using anti reflection glass the past 6 months instead of anti newton glass, and I have not seen any newton rings yet. I have printed a variety of film sizes and a large variety of film stock.

I got the AN glass from focal point.

[mbuonocore]

Hello Cor, I should have been more clear. I switched because I was seeing the pattern of the AN glass. I have been using a point light source, and it was wildly apparent. However, in retrospect, my prints made with my big durst opal bulb (in a 138) are sharper without the AN glass as well.

I should also note that I'm not really sure what the humidity in my darkroom is, but I don't think it's anywhere near 60%. Maybe for a few weeks in the summer, but not ordinarily. I'm in Toronto, Canada.

[Michael R]

Generally speaking the more collimated the light, the greater the chance of things like texture or patterns on carrier glass showing up on the print.

[LabRat]

AN glass is sometimes made from different methods... There's etched glass (etched by different processes over time), blasted glass, etc... Some glasses have different "peaks" that make contact with the film... Some are a little jagged, some have smoother, more rounded "peaks"... Different films have slicker, smoother base coats, some are a little more matt surfaced... These different combinations, combined with the moisture content of the film, ambient humidity, and how much the curl of the film set while drying will produce different outcomes...

Roll films tend to curl and produce rings the most (thinnest bases)... (Esp during damp conditions...) Uneven changes in the moisture content while the film is warming from IR while in the neg carrier can cause a slight buckle that can make the rings worse...

Things that will help is to make sure you have a IR filter in your head, sometimes changing your drying process by using different final soaks/wetting baths/drying methods will affect the base surface/curl so the film makes different contact with the AN glass, for your 120 it might be flattening the film by backrolling/drying throughly it before cutting or leaving it pressed in a book, etc for at least a week before printing... And try to avoid printing on damp nights... Try different AN glasses to find one that works in your locale... And film choice with one with a different base if the problem persists... Sometimes a glassless carrier is your only option when the humidity is high... A dehumidifier in the lab can help... Or move to the desert...

Good Luck!!!

Steve K

[Michael R]

I'll offer an additional trick which can be used above the negative with plain glass. Fix and wash an unexposed, undeveloped sheet of Tri-X 320 (TXP). Cut it to size and use it as an anti-Newton ring spacer sandwiched between the negative and the top glass. Since the base of TXP is designed for retouching, the film is just "textured" enough on both the emulsion and base surfaces to help prevent Newton rings.

[Drew Wiley]

I suspect you are mistaken, Cor. More likely, due to 120 film being very curly and quite thin, it is probably not held completely flat between your carrier glasses. I live in a very damp climate and routinely use AN glass on BOTH sides of the neg. Correctly done, this in itself presents no visible effect in the print, even with very high resolution enlarging lenses. At this very time I need to check the fine adjustment on one of my Durst carriers, since given its level of precision, I realistically need to tweak it a bit when going from thick sheet film to thinner 120. Not all carriers have this option, but some of the better Durst ones do. If you can find true
Durst AN glass, originally Belgian made, it works better on small negs than generic options.

[Drew Wiley]

Michael - you can also use a thin frosted piece of mylar above the neg, provided you carefully inspect the specific piece for blemishes on a lightbox first.

[Michael R]

But Drew, re AN glass, don't you use diffusion light systems? OP seems to have a condenser setup.

Agree, frosted mylar or duratrans can work. The trick is to get mylar that is truly uniform.

[Cor]

Thanks for all the feedback, gentlemen.

Indeed I use a condensor enlarger, although the light is not completely collimated like a point source, the tungsten light is projected down by a 45 deg mirror in the L1200 head, it surely isn't diffuse.

Looking back it seems that this phenomena is only visible with Ilford HP5+, 120 (which is quite flat, and not really thin)and the FEMOCON 80 condensor, not with HP5+, FP4+, MACO IR, Fomapan in 4*5 format and the 150 condensors.

I'll see if I can get along with plain glass, I recall I had the most problems with newton rings with Tmax400, 35mm and the FEMOCON 50 in the past,

Best,

Cor

[Struan Gray]

I experienced Newton's rings in 6x6 and 35 mm with a condensor enlarger (an M601), new Durst original AN inserts, and the TMAX and Portra films. The back side of the base is smooth in these films, and the processed emulsion doesn't seem to have much relief. I found I needed AN glass both sides to avoid Newton's rings, and even then they would occasionally appear.

I wasn't making large prints, so if I couldn't place the negative so that rings disappeared I just took the glass out and stopped the lens down.

If you need the precision of a carrier with glass, coated glass inserts are worth trying instead of AN. I don't know if there were any good glassless carriers for Durst, but the sorts that tensioned the negative to hold it flat are liked by those who have them.

[ic-racer]

This may be a difficult problem to solve. As Drew suggested try different glass, maybe what you have is not the best available. Another way of dealing with this problem is like hitting it with a hammer. It does not go away but is less visible. Use the principle or Dolby-B noise reduction. When printing DENSE negatives, the long exposure minimizes the effects of spurious density on the negarive (dust, scratches, Newton rings).

[Drew Wiley]

I once had samples on hand of over twenty different flavors of AN glass, plus various kinds of optically coated flat glass. Nowadays the options are very few.
A lot has to do with the relation of the incidence of light in relation to the specific glass pattern, along with the nature of your enlarging lenses too. My approach
is to use longer than "normal" enlarging lenses whenever possible, always a diffuse light source, and have precise carriers that keep the film very very flat.
With large format negs the currently available Focal Point glass seems perfectly acceptable, even on both sides of the neg or chrome. With smaller work I really
prefer classic Durst or Omega AN glass. I also have some strangely coated Zeiss glass that I bought a box of, but have never been able to find again. Once in awhile I get a day when the combination of slick film and damp weather leaves me only the alternative of switching out my super-duper Apo enlarging lenses
for more garden-variety Rogadons or EL-Nikkors which don't have quite as meticulous an MTF. Some lenses are simply too good and pick up too much.