Printing the AN pattern

[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.