Re: HP photosmart and negatives to positives

Craig Ruff (crruff@uswest.net)
Sun, 4 Oct 1998 08:05:37 -0600

On Wed, Sep 23, 1998 at 09:44:19PM +0200, Chris Niekel wrote:
> Does anyone know a tool to convert a negative into a positive? I've tried
> a few things with the gimp, but I can't come close to the positives the
> windoze-program delivers.

Using gimp will work for color negatives. What you will be doing is
called orange mask removal. First, scan a fully-exposed portion
of the negative. For example, the leader at the front of the roll.
It will be an clear orange color. Take a rectangle and average the
color values. You may get values like R:240 G:190 B:150. Calculate the
values you need to add to the color components to get each to match
the red value. In this case the value for green is 50 and blue is 90.

Scan a negative frame. Use gimp to add the calculated green and blue
values to the entire scan. Then invert the colors to get a positve.
You may then use gimp to adjust the contrast and brightness as you like.

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