Thanks for your extensive research Frank!
BTW. I received your mail twice.
Could I ask you to try your photoshop correcting example with the BMW image
if it is not too much trouble?
> -----Original Message-----
> From: Frank Nichols [SMTP:frank@theNichols.net]
> Sent: Friday, July 06, 2001 12:40 AM
> To: Filmscanners@Halftone. Co. Uk
> Cc: Jerry Oostrom; Lynn Allen
> Subject: RE: filmscanners: Stains and Grains (was Yellow Stain)
> WARNING: The following is a rather long discussion of the "yellow stain"
> effect seen on ACER Scanwit 2720s reported here a week or so ago. I am
> posting this in hopes of getting more details on the actual working of the
> scanwit from someone "in the know" - such as optics, sensor design, etc.
> you don't have a Scanwit or if you don't have this problem you may want
> these ramblings of a somewhat inept newbie... :-)
[Oostrom, Jerry] 
> I still have the examples of this effect posted at my website
> (http://www.theNichols.net/scanner ) This weekend I will be posting a
> of methods for hiding/correcting the yellow stain effect using Photoshop.
> The methods are not perfect, but they can salvage an unusable photo in