Ctein devotes several pages to comparison of descreening methods for
removing half-tone dots in his book "Digital Restoration from Start to
Finish". This is the second edition, I have the first one.
<http://www.amazon.com/Digital-Restoration-Start-Finish-Second/dp/0240812085/ref=sr_1_1?ie=UTF8&s=books&qid=1274705735&sr=1-1>
He shows (in increasing order of effectiveness): Dust & Scratches
filter, Gaussian Blur, Box Blur and Focus Magic.
<http://focusmagic.com/> The Focus Magic results do look almost magical
in comparison after carefully adjusting the correction radius. The dots
disappear and the image is much sharper.
But if the regular grain pattern is caused by paper surface texture
pattern he recommends Neat Image which is his choice for a digital image
noise reducer. Its proper use requires adjusting the high, mid and low
frequency filters to the specific paper pattern without filtering real
detail in the image.
Chuck Norcutt
Wayne Harridge wrote:
> Does anyone on the list have any experience of descreening scanned images ?
>
> A friend wants to produce the best print possible from a scan of a printed
> photograph, it looks like it might be from a newspaper/magazine. He doesn't
> have access to the original but has a scan made by the State Library of
> Victoria as a starting point. The print screen seems to be pretty well
> resolved in the scan which was done at 300dpi from the approx. 10"x8"
> printed image.
>
> I have uploaded the scan here:
> http://lrh.structuregraphs.com/images/roper.jpg (about 6Mb)
>
> Any suggestions welcome.
>
> ...Wayne
>
> Wayne Harridge
> http://lrh.structuregraphs.com/
>
>
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