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Scanning a printed image

From: Scanning with SilverFast

Video: Scanning a printed image

In this video, I'd like to address a very specific kind of scan, and that is scanning an image that's already been printed on a printing press or a laser printer or something like that. The difference between a printed image and a photograph is that the photograph is pretty much continuous tone, that is you can't see the structure in the image. Whereas a printed image has an actual pattern of halftone dots. I've already done a prescan here just to kind of move the process along a little bit and you'll notice, if you look in the background, you can see the pattern. That pattern is the pattern of halftone dots that has been captured by the scanner.

Scanning a printed image

In this video, I'd like to address a very specific kind of scan, and that is scanning an image that's already been printed on a printing press or a laser printer or something like that. The difference between a printed image and a photograph is that the photograph is pretty much continuous tone, that is you can't see the structure in the image. Whereas a printed image has an actual pattern of halftone dots. I've already done a prescan here just to kind of move the process along a little bit and you'll notice, if you look in the background, you can see the pattern. That pattern is the pattern of halftone dots that has been captured by the scanner.

In this particular video, our primary issue is going to be descreening and that is taking out the screen pattern that results from scanning a halftone image. If you don't take out this pattern and you reprint this, it looks much worse than this, because reprinting an image that hasn't been descreened creates all sorts of imaging nightmares called moire patterns, which can be two or three times as obvious as what you see here. First, let's just go ahead and talk about the setup reflective and positive 24 bit, and we've done our prescan, so we can move on. I am really not focusing on correction on this particular image.

So let's just do an auto correct. It actually did a pretty nice job of improving brightness and contrast. Let's go ahead and label our image. We're going to call this FruitPunch. It's going to be an RGB image, and then we're going to do this at 300 pixels per inch. And as always, we're going to save this out in an uncompressed format that we can then make duplicates of and save out in other formats and other dimensions and linear resolutions later on. In this case, I'm going to assume that I'm probably going to take this into Photoshop and maybe do a few other things with it.

So I'll save this one out as a .PSD file. Now in terms of the framing, if I know I'm going to reprint this and I know what dimensions I want to reprint it, like 5x7, I can go ahead and choose 5x7 and then by choosing that format, it's all automatically going to give me a 5x7 frame that I can then take and just resize, like this. And notice when I choose 5x7, it automatically puts 5x7 in the output and it locks that 5x7 output.

That's the same thing as checking the check box in that Print Output Task in the Automatic mode. All right, so we're starting with a 2x3, we're going to end up with a 5x7, we're going to choose 300 pixels per inch for our scan. We've done our automatic correction and we can edit that if we choose to, but what I really want to show you is this tool called the Descreening. And notice we can access this image and look at various portions of the image by moving around the navigator. And here, you can very obviously see the halftone dot pattern and you can see the results of the descreening taking that out.

On the left side of the navigator, the descreen pattern is very obvious, but in the preview from the descreened, we can see how that has been taken out. Now, let's go down and actually access the Descreen dialog box and see how this actually works. Typically, you would start here with presets and notices these two presets currently; Retain text (Newspaper), Retain text (Magazine). If you're not sure where this came from, choose one and then see how it looks. We're going to choose Magazine and then guess at the LPI, in this case, say, 133 line screen. Then we can move our preview around to see the impact and than we can adjust the Softness.

For instance, if we take this all the way up here to 10, which is fully soft, notice the image gets very, very soft. If we take this all the way down to 1, far less softness, but you start to see the halftone dot pattern. You can experiment, say, try the Newspaper 85, and notice that does a little bit better job than the Magazine and we didn't have to increase the Softness very much. We'll go with Newspaper just with the Softness of 1 and we might end up with a little bit better looking image with less reduction in the overall sharpness of the image.

And at anytime, you can click on that preview and come in and take a look at that image. So if we were at the Magazine, if we decided, if we really did print this in a magazine and we move this to, say, 2 and take a look at it; move it to 3 and take a look at it; move it to 4 and take a look at it. Notice that, progressively, that pattern disappears. By the time we get to number 5, it's completely disappeared and you can compare that against what you got at the Newspaper 85 and 1.

I think using the Magazine at 133 with the Softness of 5, we actually end up with a little bit better contrast and sharpness in the image. So you can experiment with those settings to get it just exactly the way you want it. Then we're ready to go ahead and scan the image. I'm going to click on Scan and you can follow the scan process in the Scanner status dialog box. It's going to scan the image and it's going to apply the descreening. So, once the scan is finished and the descreening is applied, we can click this Open image file and take a look at the finished version of the image.

Now we are not quite done yet. Let's disable the descreening and everything else exactly the same way and let's apply the same scan. Boy, you can really see the halftone dot patterns. These are called rosettes that are formed by the cyan, magenta, yellow, and black inks there are applied to its specific screen angles. Once again, after the scan finishes, we'll open this up and we can compare. We notice how we've completely removed this rosette pattern and really been able to retain a good deal of the overall sharpness of the image. Is this one as sharp as this? No, but if we try to reprint this one on any sort of a printing device that's going to create a horrible nasty moire pattern which will be super, super obvious.

So that is descreening images using SilverFast.

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This video is part of

Image for Scanning with SilverFast
Scanning with SilverFast

52 video lessons · 4320 viewers

Taz Tally
Author

 
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  1. 5m 19s
    1. Welcome
      58s
    2. What you should know before watching this course
      43s
    3. Taking the Tazmanian Oath
      3m 38s
  2. 19m 14s
    1. Launching SilverFast
      4m 2s
    2. Touring the SilverFast interface
      3m 35s
    3. Understanding SilverFast's scanning workflows
      4m 28s
    4. Using automated vs. manual scanning
      4m 31s
    5. Getting help as you use SilverFast
      2m 38s
  3. 32m 46s
    1. Touring the SilverFast 8 automatic scanning tools
      6m 7s
    2. Preparing for automatic scanning
      4m 6s
    3. Arranging your workspace
      4m 23s
    4. Setting up color management
      4m 43s
    5. Setting scan frame and resolution
      3m 55s
    6. Adjusting, naming, formatting, and locating an image
      8m 24s
    7. Previewing scan settings with the info tool
      1m 8s
  4. 1h 7m
    1. Scanning simple line art
      8m 6s
    2. Scanning detailed line art
      8m 9s
    3. Scanning grayscale photos
      11m 43s
    4. Scanning color photos
      11m 17s
    5. Scanning a color photo as a grayscale image
      12m 15s
    6. Scanning a positive piece of film
      6m 52s
    7. Scanning a negative piece of film
      8m 39s
  5. 26m 1s
    1. Touring the manual scanning tools
      7m 19s
    2. Setting preferences for manual scanning
      10m 0s
    3. Calibrating your scanner
      3m 40s
    4. Arranging your workspace
      5m 2s
  6. 1h 35m
    1. Scanning simple line art and changing it into vectors
      7m 38s
    2. Scanning simple line art and keeping it as pixels
      5m 41s
    3. Scanning detailed line art
      8m 18s
    4. Scanning grayscale photos
      14m 5s
    5. Scanning landscape color photos
      15m 51s
    6. Scanning color portrait photos
      13m 56s
    7. Scanning color product shots
      9m 29s
    8. Scanning a color photo as a grayscale image
      4m 31s
    9. Scanning a piece of positive color film
      5m 52s
    10. Scanning a piece of negative color film
      9m 56s
  7. 1h 0m
    1. Should I use SilverFast or Photoshop?
      4m 9s
    2. Making global color corrections
      4m 37s
    3. Bringing out shadow details
      4m 28s
    4. Making a selective color replacement
      3m 21s
    5. Sharpening in SilverFast
      7m 15s
    6. Working with target-based corrections
      4m 55s
    7. Color correcting with neutrals
      10m 19s
    8. Exploring automatic color correction in manual mode
      3m 35s
    9. Scanning a printed image
      5m 49s
    10. High-bit-depth and HDR scanning
      5m 28s
    11. Removing noise and patterns
      3m 32s
    12. Removing dust and scratches
      3m 30s
  8. 7m 2s
    1. Batch scanning images
      1m 28s
    2. Using the JobManager
      4m 16s
    3. Exploring SilverFast 8 shortcuts and tips
      1m 18s
  9. 1m 29s
    1. Goodbye
      1m 29s

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