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Newton Rings on Image Scans

Pablo Ledesma , Dec 19, 2004; 04:11 a.m.

Please look at this scanned pic and answer a question for me; are the woodgrain patterns in this can that Newton effect? Would anti- newton glass fix it? I wasn't getting sharp results from my negative carrier, or my self developed neg's weren't drying flat enough, so I placed them directly on the scanner glass with a piece of glass over them. Am I on the right track? thanks for your time.

Pablo


Newton?

Responses

Pablo Ledesma , Dec 19, 2004; 04:14 a.m.

Response to Newton?

err... "woodgrain patterns in this can that Newton effect?" should read; woodgrain patterns in this scan that "Newton effect"?

Thanks Pablo

Ilkka Nissila , Dec 19, 2004; 05:38 a.m.

Response to Newton?

Yes, those are Newton's rings.

Anti-newton glass may cause a granular pattern in the scanned file which is even worse than rings. If you cannot ensure flatness without glass, you may want to try a fluid which matches the refractive index of the glass. Which scanner are you using?

Daryl Walter , Dec 19, 2004; 05:54 a.m.

Response to Newton?

Hi Pablo. That definitely looks like a diffraction pattern and the description of how you scanned this image would fit with the pattern being of the 'Newton's rings' variety. Newton's rings usually form due to interference created by reflection of light from a flat surface onto a spherical surface. In scanners moisture on either the negative or on the glass surface (the tiny spherical droplets of moisture are responsible for the concentric rings in the pattern) can result in this problem. In theory you can avoid this by making sure that everything is very dry. This may be possible if you live at very high altitude but in practice it isn't easy to get things as dry as they need to be. This is the reason that most transparency scanners use specially designed neg. carriers and the reason that they don't support scanning of glass-mounted slides. Your scanner should compensate for the non-flatness of your negatives by doing a prefocussing run but if this isn't working then perhaps you coudl try manual focussing? (depends on how good your scanner is I guess). Alternatively I wonder if you could scan the slide in two different directions and combine the results? Anyway, the short answer is 'Yes' it is that 'Newton effect'. Sorry I can't be more helpful with a solution. Daryl P.S. Are you sure the sharpness problem isn't lack of focus in the original negative? Nice cat! (I thought Newton was his name when I first looked at your post :) )

Pablo Ledesma , Dec 19, 2004; 07:18 a.m.

Response to Newton?

I'm using an Epson 3170, Well sometimes it is my focusing, sometimes its my developing, sometimes its... I see a pattern... I would assume that a millimeter or half worth of curve in a neg in a carrier would affect the focus across the scan, right? Would thin piece of clear or white opaque plastic work? The Med. format carrier has a white opaque plastic door which shuts over the neg maybe it would work directly on the glass...

Edward Ingold , Dec 19, 2004; 12:31 p.m.

I get Newton's Rings with a glass carrier in a Nikon LS-8000, despite having anti-Newton glass. They result from interference patterns generated between two reflective surfaces in close proximity (not from water droplets). Since I scan only 6x6, I placed one of the self-adhesive strips in the Nikon kit on the upper glass, between the first and second frame of the film strip, to increase the spacing. This eliminated the Newton Ring formation.

You could use a strip of self-adhesive label to do the same. You might want to cut a mask from black craft paper or matting board to locate the film, and hinge the cover glass to the mask. That works pretty well with my Epson 2450.

The lower, emulsion side of the film is less reflective, and usually curled away from the glass, and is less likely to form Newton's Rings.

Neil Parker , Dec 19, 2004; 12:50 p.m.

Edward is right, moisture has nothing to do with it, it is the interference pattern caused by the contact of 2 smooth surfaces. With B/W silver-based film you can flip it over so that the rougher emulsion side is in contact, a good chance that will eliminate most or all of the newton rings. If not, space it away from contact, but focus may be off with something like an epson flatbed that has no focus adjustment and relies on depth of field.

There are also some fine powdered products (sorry can't remember a name) that are designed to be dusted on the glass surface and prevent newton rings.

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