filmscanners: Re: Dust in Sprintscan 4000?

[Roger Smith <rsmith@unb.ca>]

At 3:26 PM -0700 9/20/01, Arthur Entlich wrote:
>But, is it possible scanner CCDs are responding to some information
>which is normally outside of the "visual spectrum", or are, due to some
>type of lighting or optics issue in the use of separation filters,
>emphasizing defects in the emulsion or base layers (perhaps microscopic
>air bubbles or density changes that show up as defracted light patterns)
>which end up looking like "spots" or dots on the scan? For instance, I
>notice some films, when viewed on certain angles, have an almost
>crystalline quality to the base surface.  This is not, as far as I've
>been able to determine, a residue on the surface, but something within
>the structure of the film base itself.

        Art, I think you are correct. The images I posted recently 
showing a fine "bubble" structure in the film base surface, and how 
it affects a 2820 ppi scan, would seem to support your observations.

Regards,
Roger Smith