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Qstn about using Epson CX5000 to scan pix

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powderburner

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I am really hoping that we have some computer/printer experts hanging around here that can tell me why--

When I use my Epson CX5000 (no endorsement implied) to scan pix on a really high dpi setting (Epson scan software on a Vista PC) I get wide bands of altered colors, fine diagonal bands of light/dark, and other changes to the original picture?

I have tried every setting I can find in the software. Currently I have selected "magazine", "color", resolution "150", with standard settings for brightness etc.

The next setting I am considering is 12 gauge

Can anyone help?
 

Reinhard

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Hi,

what kind of source image are you trying to scan? Was it developed from film (fully analog process) or is it some kind of raster graphics (some printing processes, typically digital)? What happens if you rotate your image in varying degrees? What happens if you try to scan you're handwriting a piece of balsa (to be rocketry related ;)) or anything else that was not rasterized with the same settings.

Your description sounds like you're dealing with aliasing artifacts to me but this will only happen with a rasterized source. If you can't reproduce your error with an analog source or your diagonal bands change significantly with small rotations you might try to find an antialiasing program for images (not sure if something useful is available).

Reinhard
 
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powderburner

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Yeah, I forgot to note that. I am trying to "read" pictures from magazines. They are mostly good-quality publications but they are not original photographic prints.

I don't know how magazines print their pix these days, or what it means if the pictures are digital, or how that interacts with the scanner. All I know is that I get some funky colors and "noise" when scanning at high resolutions (trying to pull out details from the pictures).
 

troj

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Yeah, I forgot to note that. I am trying to "read" pictures from magazines. They are mostly good-quality publications but they are not original photographic prints.

I don't know how magazines print their pix these days, or what it means if the pictures are digital, or how that interacts with the scanner. All I know is that I get some funky colors and "noise" when scanning at high resolutions (trying to pull out details from the pictures).
Your problems are caused because of the magazine source. Think of a picture tube, where each "pixel" is actually multiple dots, very close together. Magazine screens are similar.

Your scanner is picking that up, and it's affecting the scan.

-Kevin
 

Reinhard

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Well, this pretty much sounds like aliasing. To get rid of this problem, you can do two things: Increase the resolution of the scan or to reduce the resolution of the source.

Increasing the resolution of the scan is limited by the scanner hardware, in your case 1200x2400 dpi. Higher interpolated resolutions are useless, because they use the "distorted" original data.

If you're already on the limit of the scanner, you can try to decrease the resolution of your source by blurring it. You don't need to disfigure your images, its just necessary to reduce the resolution to about 600dpi which is still pretty high qualitiy stuff unless you want to enlarge the image.

To blur the image, you could put one or multiple layers of translucent paper between the image and the scanner. A pane of glass might work to (increasing distance, bringing image slightly out of focus therefore blurring it).

Photographing the image can yield pretty could results to. Misaligning focus is pretty easy in this case and you have the option of varying your resolution in relation to your source (zooming, or changing the distance) which might do the trick.

Last but not least, you can try to rotate your image. If this works, you can rotate it back in software. This is not exactly anti-aliasing, but if you're lucky, the artifacts may be less noticeable.

All of this, I haven't tried for my self, so I have no idea ho well this will work in practice.

Reinhard
 

bobkrech

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From http://www.scantips.com/basics06.html

Moire patterns
This interference is called a moiré pattern (pronounced more-ay). In a scanned image, Moiré patterns are caused by interference between two sets of fine pattern grids, the scanner samples and the halftone screen in the original image. Any scanner will do this, it's a simple fact of life.

Read the rest of the article to see how to get around it.

US Currency is designed to give moiré patterns when scanned to prevent counterfeiting by conventional scanner.

Bob
 

Pat_B

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I deal with dozens moire problems a few times each year when I lay out an ad book for some work I do.

One quick and easy thing to try is to scan your image into your software program (I use Photoshop) the rotate it a few degrees; then rotate it back to where you started from. Be sure to rotate it manually or at least type your rotation angle in a dialog box- do NOT just use the UNDO command.

The algorithim that calculates the redrawing of the pixels for a rotation command is a little bit arbitrary in that your final image will not be the same as when it started. That subtle shift of the pixels is just enough to destroy the moire pattern.

Can also try a slight blur command then resharpen. Again, you somewhat end up where you started but it's enough of a change to the image so as to destory the moire pattern.
 

Trident

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If all else fails, buy a piece of sh$% Lexmark multi-function inkjet. My was $29 at Walmart, and never printed worth a darn. The scanner probably would work for you, because it is so cheap it probably cannot take advantage of the Moire effect ...

:rolleyes:
 

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