All of a sudden, newton rings..

[Jrewt]

I have a durst laborator 1200 that I use for MF and 4x5 that is now giving me newton rings on ALL of my medium format negatives. The negatives are between two glass inserts in the carrier, which has never given me any problems until now. I'm not sure if AN glass is available, but I'm sure I could get some cut. My concern is that I will see the pattern of the AN glass on the prints, does anyone have any advice on AN glass with this particular enlarger?

Cheers

[ic-racer]

AN glass is certainly available. Sometimes the glass comes up for sale on Ebay ( http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&item=320677418138&nma=true&rt=nc&si=MKJ6be8zVy7rasSoMTx%252BBLB0sBw%253D#ht_2620wt_1267) . KHB, can probably get it and fpoint is also a source.

With a diffusion head I use AN glass for minox, 16mm, and 35mm without seeing any pattern. I usually use glassless with 4x5 because the film is pretty thick and stays very flat for me.

You did not say which head you are using.

[Drew Wiley]

Depends. Not all AN glass is created equal. It depends not only upon the glass type,
but on the angle of incidence of the light rays, the degree of magnification, how
shallow your depth of field is (film plane flatness vs how far lens is stopped down),
even on the MTF of you enlarger lens. I have found the original Durst AN glass to be
particularly good, as it has a kind of wave-like pattern to it, rather than a grainy one. For my large format work, I've also found Focal Point glass to be problem-free;
but have never tried it with small negatives (for which I use a completely different
enlarger). I generally use AN glass for both the top and bottom of color chromes and
negs, or bottom only for most b&W negs (except real slick negs like TMX or Tech Pan). I use diffused light on all my various enlargers. But I do live in a coastal climate where newton-rings are a constant nuisance. The idea of going glassless
seems like sheer barbarism, however (I like sharp prints).