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Re: filmscanners: RE: filmscanners: nikonscan

In a message dated 10/9/2001 2:13:38 AM EST, bill_sub@billfernandez.com 

> >>From what Ed has said in the past, the focus position seems to be in one
>  >direction only - I *think* along the length of the film.

On scanners where VueScan does the focus itself, I read one scan
line in the middle of the scan area and adjust the focus position
until the contrast is at a maximum.  The entire scan line is used to
compute the contrast, and I use the sum of the absolute values
of the difference between adjacent pixel values to compute
the contrast.

On the Nikon scanners, I send the scanner the X,Y position
of the focus (in the center of the frame).  I'm guessing that
it adjusts the focus position until the contrast is maximized
in the region around this X,Y position.

Ed Hamrick


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