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[filmscanners] Re: Grain from negs with Multi Pro

> You mention unsharp mask.  I really don't know how this feature should be
> used (I don't have docs with PS).  I commonly use about 50 in usharp mask.

There are 3 variables:


      the distance in pixels that the algorithm inspects to decide whether
it should sharpen. Note the radius need not be an integer - I usually use
about 0.9 with my digicam but 1.4-1.8 with the scanner. If I have up-sampled
an image from the optical resolution then I increase the radius and
conversely if I have down-sampled an image I decrease the radius.

      is the required difference in values of pixels within the radius that
is required to trigger the sharpening.

      is how much sharpening effect should be applied to the pixels selected
by the combination of radius & threshold

Increasing radius or decreasing threshold will reduce the value for amount
that a picture can tolerate.

Decreasing radius or increasing threshold will increase the value for amount
that a picture can tolerate.

To avoid sharpening grain and/or noise you need to set threshold higher the
variance in values caused by grain.

To sharpen everything a bit you should use a smaller radius a larger radius
will only effect more significant boundaries (more edge sharpen than overall

For images that I am printing I usually view the image at a size around
1.5x-2x actual target print size

It's sometimes advantageous to sharpen an image twice - once to gently
overall sharpen and once to add slight extra sharpening to the edges.


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