Book page scan gradient

Dear PhotoShop Group,

I have a page I scanned from a book. Near the spine the page gets gradually darker because the page is getting further from the scanning plane (I can't lay it flat). Does anyone have an idea about trying to measure and compensate for this gradient so the page appears evenly illuminated. Thanks in advance!

Tom
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Tom Kinter 507-284-4981

Mayo Foundation Rochester MN 55905 USA

http://www.mayo.edu/ultrasound
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"Tom Kinter" wrote in message

Dear PhotoShop Group,

I have a page I scanned from a book. Near the spine the page gets gradually darker because the page is getting further from the scanning plane (I can't lay it flat). Does anyone have an idea about trying to measure and compensate for this gradient so the page appears evenly illuminated. Thanks in advance!

Tom, very often it is best to just remove that area and fill it in with a modest gradient layer over a properly shaded fill color. If you would like to post the image for the rest of us, or send it to me I will look at it.

(Done as a favor to a Mayo associate.)
jjs in Winona

Does anyone have an idea about trying to
measure and compensate for this gradient so the page appears evenly illuminated.

Make a feathered selection of the dark page, with the amount of the feather equal to the width of the gradient, and use Image->Adjust->Curves to lighten the dark part of the scan.
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(Tom Kinter) asks:

I have a page I scanned from a book. Near the spine the page gets gradually darker because the page is getting further from the scanning plane (I can't lay it flat). Does anyone have an idea about trying to measure and compensate for this gradient so the page appears evenly illuminated. Thanks in advance!

Duplicate the image. Use the Filter->Custom->Maximum function to replace each pixel with its brightest neighbor. Adjust the radius according to the width of your characters. Under the reasonable assumption that the text is always darker than the LOCAL white page, this will erase the text and leave an image of the brightness variation due to curvature and lighting. Subtract this image from the original.

For more ways to handle this (common) problem see the tutorial at http://www.reindeergraphics.com/tutorial/chap2/defect06.html