A few years ago I was able to scan (at a high resolution, yielding 23 MB TIFF files) a collection of old picture postcards, mostly early 20th century town and city views, before they were auctioned off on eBay. It was probably my mistake not to fool around with the scanner's descreen feature, because though I didn't take it seriously at the time, I was left with faint diagonal lines running through most of the images - as the printing process involved using those tiny dots of color (halftones?)
Can this problem be fixed? A motion-panning test with various video applications still showed these lines - and they moved when tracking in and out. I just don't know if I can digitally descreen the images now, after they've been scanned, or if I'm out of luck here. Photoshop doesn't seem to have a descreen filter, and please don't suggest the video de-interlace, as it doesn't do anything, nor blurring of any kind, as I need the detail. I'm sure printing the picture out wouldn't help either.
Help would be highly appreciated!!
#1
Keith,
There was a thread about Moire patterns a while back ... you may find some useful information in it.
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http://www.adobeforums.com/cgi-bin/webx?128@@.2cd1250f>
Hope this helps
Wendy
#2
Thanks Wendy,
The possible solution, the moire removal technique, seems to involve a plug-in for PS 6, but possibly not PE, which I have. It also involves a lot of steps. With somewhere around 150 images, I'd have a project lasting several months! My other thought now is to try finding a scanner-users forum to find out if descreening can be applied after scanning, or if the scan can somehow be reversed.
Keith
#3
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http://www.scantips.com>
If you scroll down that page, there's a Search box. Type in "moiré".
#4
Ramon,
Glad to see you're still spying on us ! <G> Is that you behind that bush ?
:-)
Brent
#5
Behind a Bush? Me? Why, never! B)
#6
I am glad Ramon is lurking around too!
#7
Here's another response I received over this issue from another forum:
Moiré effects result from mismatching any two grids. It's a WYSIWYG process -- once you got it, you got it.
If there's no other way to get the same images, you may try it with this:
To get the moiré matching your grid, adjust the resolution of your images (Photoshop: Image size/Resolution)
Most likely you have overscanned these images... Today 80 lines/cm (=305 dpi) is standard. Scanning such an image at a much higher resolution which isn't a multiple (i.e. 610, 915...) of the printed resolution will result in visible moiré. Hunting for the correct resolution is a non-reversible process, so if you got it wrong, undo, and restart with a different resolution. Once you found the match, you're done. Hopefully you're able to use the resulting (smaller) images. If not, try this one:
In Photoshop, apply "Interpolate brightness" from "Distortion filters". Set the number of pixels until your image looks best.
As a second step, you may add some distortions and/or apply an unsharp mask.
Guess it needs some tweaking to get the first image look good, but most likely the very same settings will work for all of your images. Set up an action in Photoshop and process your images in no time once you got it right for the first one.
#8