Converting Halftones back to Grayscale

I have scanned in some family photos from of a book printed in 1978. The B&W photos were printed using the halftone method; resulting in a conversion of the now-lost original (B&W/grayscale) photos into halftone photos comprised of various sized dots.

The photos in question are those of a friend's direct ancestors and were taken in the mid-1800's.

I would like to "convert" the dots making the photos back into "regular" grayscale photos so that he may have 'traditional' photos of his ancestors.

Has anyone found a method to make such a conversion back from halftone?

Thanks,
Mike Gaudet --

First, you should see if your scanner software has a "descreen" function.

If not, try the Median filter. I find it's best to scale the image up a bit first, because the Median filter can only be set for integral pixel diameters. Scaling up first, and then scaling back down when done, effectively gives you fractional values.

The scanner software's "descreen" function will give much better results, though.

Also see the Form FAQ on Descreening