[Leica] Re: Solutions for avoiding newton rings

[Jim Brick <jimbrick@photoaccess.com>]

Newton rings are caused by imperfect contact by part of the film with
glass. Film with more curl are more prone to newton rings. Current humidity
also is a factor as to the severity of the problem.

One solution is, of course, to eliminate all contact between film and
glass. This is why glassless neg carriers are so popular.

Many years ago (1950's) Kodak recommended rubbing the glass (that which has
contact with the film) with fine (00) pumice powder using cotton. This
basically makes the surface layer of the glass, less "glazed" so that the
type of film/glass contact, producing newton rings, does not take place.
The use of 00 pumice powder makes no humanly observable difference. But it
makes a difference in how the film base and glass get along.

Jim


At 09:59 AM 3/1/00 +0200, FB wrote:
>Thanks a lot for your help in solving my newton-ring problem.
>First of all I was wondring why Leitz made enlarges which were Newton 
>sensitive. The answer is that they were not newton-sensitive with the 
>emulsions of the 50's and 60's. They were not that thin and glossy.
>The solutions can be divided in two groups :
>1. Anti-newton glass
>- Leitz anti-newton glass but the Leitz anti-newton glass is hard to 
>find (impossible ?)
>- Make anti-newton glass yourself with the AN-glass of a 6x6 slide 
>frame. That must be a good solution but glass doesn't cut as easily as 
>paper and make sure the edges do not scratch the negative.
>2. Avoiding contact between the negative and the condensor.
>- Tape of the 24x36mm frame and make sure the tape is not too thin 
>(the misake I made).
>- Make a frame to put on the negative stage with a 24x36mm cut out. I 
>made it out of medical film.
>I am working with the last solution now which works very well for me. 
>I also have the feeling that it is more forginving for dust on the 
>negatives.
>Greetings,