This is something that has bothered me for a while and I hope somebody can help me with it. I often get these lines when I scan images (see attached image) and I have no idea how to remove them or prevent them. I’ve heard that sometimes these lines and faults are from the way the image is printed and that there is a way to remove them. These ones seem a little different.
Can anyone please help me, or tell me where to look? Is there a term for these lines that I can read up on?
I’ve just scanned a whole bunch of beautiful photos from an architecture book and I’d really like to be able to fix them up.
That’s a moire pattern.
Google on ‘moire pattern scanner’ to find some pages that talk about the cause and some solutions. One solution is to scan at the highest possible resolution.
Wikipedia has a page that talks about what a moire pattern is: moire pattern
One of the external links in the Wikipedia article talks about how to remove more patterns from a scanned image.
Preventing is better, the Dutch even have a saying to that effect. Or, well, removal very early in the process counts as preventing right? My scanner has a setting called “Descreen” which I can check (or uncheck) before making the scan. It is designed to ‘prevent’ such moire patterns and does quite a good job, but scanning takes a lot longer (like 3 times as long). With my previous scanner, I used to rotate an image over 1 degree, then rotate it back, then crop. Quite tedious, and not as good, because it introduced a fair amount of blurr.
Either way, as a bonus, a jpg takes less space because there is less (unwanted!) detail to compress.
Interesting. I haven’t used a scanner that has that kind of feature or I’ve just been unaware that it was a feature. I don’t do much scanning and haven’t had to deal with moire patterns in scans.
My scanner also has a feature I select to prevent moire. Andrew, if your scanner has a setting for scanning magazine images/paper, try using that one. I think moire patterns are caused by the glossy sheen on those pages because that’s the only time I get moire.
The moire pattern results because the magazine and book images are made up of small individual dots. It’s the way they’re printed. Look at a photo in a glossy magazine under a good magnifying glass and you’ll see the dots. The scanner also sees those individual dots and if they don’t line up perfectly with the scanners scan lines and dots then you get moire patterns.
Images that are made on photographic paper or a dye sublimation printer don’t have the dots because the printing process is completely different. You can scan a digital photo and you won’t get the moire patterns.
