Re: RBT Mounts

[P3D emdesher <emdesher@xxxxxxxxxxxxxxxxxxxx>]

On Mon, 11 Nov 1996, P3D Ronald W Doerfler wrote:
 
> Also, I meant to ask if anyone thinks the anti-newton glass makes the image
> less sharp than an image in "plain glass" (like that from Reel-3D for Albion
> masks), not less sharp than "no glass."
> 
> Ron Doerfler
> 
> 
In theory, yes.  The purpose of the anti-Newton surface treatment is to 
physically separate the inner glass surface from the film surface.  
Newton's rings appear as multi-hued rainbows in the slide.  This effect 
is the result of film touching a glass surface.  Try gently squeezing
a glass mounted slide together, and you will see the Newton effect.  A 
number of possible solutions have been tried over the years, but the best 
way to avoid this problem is to straighten the processed film before 
cutting and to use anti-Newton glass.  Some areas of the country seem to 
be more prone to Newton's rings account of high humidity causing the film 
to curl.  The trade-off for using anti-Newton glass is a slight loss in 
image quality-remember you are using a diffused glass surface.  Indeed, 
the problem is to select just the degree of glass treatment needed to 
prevent the rings while minimizing resulting image softness.  The RBT 
mount, because it was designed to place glass in direct 
contact with film, has to use anti-Newton glass, otherwise annoying 
rings would certainly result.  To what degree the projected image is 
softer for having used anti-newton glass instead of regular glass, 
depends on how critical you are.  Dennis Sherwood


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