Re: [Gimp-user] Fw: scan-mirrage-effect-Problem with postcard

[Gene Heskett <gheskett shentel net>]

On Monday 10 May 2021 20:56:27 Rick Strong wrote:

> I didn't see my reply show up on the Gimp user list.
> RS
> -----Original Message-----
> From: Rick Strong
> Sent: Monday, May 10, 2021 11:33 AM
> To: Tim (from Hamburg) ; gimp-user-list gnome org
> Subject: Re: [Gimp-user] scan-mirrage-effect-Problem with postcard
>
> Well, it's not moiré from the glass.
>
> It seems to be a scanning artefact introduced by the scanner. But you
> say it doesn't happen with scans of images on plain or matte paper.
> try putting a black card over the postcard before you lower the lid.
> Also check your scanner settings.
>
> If that doesn't work, you could try photographing the glossy postcard
> with a camera. With some fridge magnets you could stick it vertically
> to the side of something metallic in good light, like your
> refrigerator or your car. Then crop out or clone out the magnets from
> the photograph.
>
> Rick S.

The moire pattern is without a doubt, from scanning a litho print which 
is microscopic patterns of different size colored dots that mix in the 
eye to make the color. If the scanner or camera lens is sharp enough and 
the autofocus accurate enough, it can be quite a problem. you may be 
able to reduce or eliminaate it with what ever is in the toolbox to 
reduce the unwanted sharpness, which should blend the dot pattern away 
if done in the right amount and size of the blend. Ideally, the size of 
the blend should match the size of the dot pattern but tolerances in 
paper positioning as the printer lays each ink color may make this 
difficult to balance without adversly effecting the overall sharpness.

Be aware that copyright info may be hidden, invisible to the eye in this 
dot pattern.  And it is considered valid proof of a violation.
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Cheers, Gene Heskett
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