I have read the Feb '98 postings about these cursed things, but my problem is that I have a Focomat enlarger and the setup does not involve a glass carrier. Rather, the autofocus arrangement brings the lower surface of the condenser lens directly into contact with the negative. The rings show up towards the edges along the long sides of the negative, rather than in the middle or short edge areas. Any thoughts on remedies?

Thanks, as always.

Shelagh

-- Shelagh Mathers (smathers@sympatico.ca), February 06, 2001

Answers

I used to use an 'Envoy' enlarger with a similar design - the condenser acting as the pressure plate for the negative. I cut a thin (~0.5mm) circular aluminium plate to the same diameter as the condenser, with a 24x36 mm aperture for the negative, and placed it under the condenser. Problem solved.
A black paper mask would work just as well, but a little less precise and permanent.
If you're going to make a metal mask, ensure that the edges are smoothed off to avoid any posibility of scratching the film, and spray it matt black.
Absolute negative flatness is all very well in theory, but Newton's rings are impossible to ignore in the print.

-- Pete Andrews (p.l.andrews@bham.ac.uk), February 06, 2001.

You can easily cut an overlay mask from a piece of 4x5 or larger film, exposed and developed black. This was a cheap fix for Newton Rings on Focomat and Valoy enlargers that was published in the Leica Manuals in the 50's. The Newton Rings tend to be worst when your film is "green," fresh from drying, and sometimes a more complete film drying period can help. You may need to refocus when you use the mask, because the autofocus is shifted a bit by the mask. As you probably know, Leitz made both a metal mask and a ground glass accessory to slip over the condensor to cure the Newton Ring problem, but both of these widgets are long out of stock and expensive on the used market. Easy problem to fix on your own, though. Good luck! Tim Nelson

-- Tim Nelson (timothy.nelson@yale.edu), February 08, 2001.