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[filmscanners] Re: Background Film Grain

This is where the threshold number comes into use.  Threshold amount
determine the degree of variation of nearby pixels necessary before the
USM feature is made functional in that area.

So, areas that are of smooth gradients (like out of focus areas) will
have less variation than sharp line changes.  If you bring the threshold
up to 6-10, for instance, the USM algorithm will be ignored in the more
out of focus areas, while still functioning where higher variation
between areas exists.

You will find you need to move the threshold and radius to find the best


HMSDOC@aol.com wrote:

> Most of my images are scans from slides or negatives made at 4000ppi.  I find
> that to get the main focused subject of the image sharpened with USM I also
> get marked sharpening of  the grain in the out of focus background, which
> detracts from the image.  The main subject, which is in focus, does not seem
> to have a significant problem with grain.  What is the best method of
> adequately sharpening an image and yet keeping the background smooth and not
> overly grainy appearing??  Any help would be appreciated.
> Howard

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