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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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