Preserved Topic: Improving scanned images (Page 1 of 1)

Hello. Something I can't figured out in PS is improving scanned images. What bugs me in this images aret he dots. How can you get rid of them and/or what would you advise to improve scanned images?

Example image can be seen here: http://random.cynicallyinsane.net/summer/2/summer_46.jpg

I'd be glad to hear your ideas.

kensai: It depends on what you are scanning from in the first place. If you are scanning from a nice glossy image then you'll get a better quality scan - that looks like you got it from ordinary (insert technical terms) and the dots are part of the original printing. If it isn't then you should be able to increase the DPI settings when you scan it in and that will give you a smoother/cleaner image (and a much larger file size). I don't see it being a PS problem uite yet - more of a problem with the scanning and/or the quality of the original.

I'm sure someone will be along in a minute with some better tips

___________________
Emps

FAQs: Emperor

Looks like you're scanning from a screened print (i.e. a magazine, vhs cover, back of a toy box, etc.) Those dots look to be halftone screen patterns. Not much you can do about getting those to not show up in the scan, as they are actually part of the original image. The first/quickest thing you can do is try adding a slight bit of a median blur to the image (filters>noise>median). This only works well with images like that (anime'/cartoons) because they have lots of flat color to them. Adding a slight median blur will even out the colors in the halftone screen and should make them into an average color (hense the name median hehe). The amount to do it depends on the image, so I suggest just playing with settings, but when I've tried to clean up anime' pictures before, media has worked wonders for me.


Whatever doesn't kill us...
Is probably circling back for another try.

I do believe Moiré is the word for that effect. To fix it you could use smart blur and various other filters.
When scanning set the DPI high and the size to a low percentage.

If I'm not mistaken, an old trick is to scan it at a 45degree angle and then rotate the canvas in PS back to where it should be. I've heard that helps with moire.

The proper angle would be 15° degs, cyan in generally the most common primary. Black 45° in most cases is so slight that the morie has little effect. But you would want to angle the scan to match most noticable primary.

Generally halftone screen angles are at the following.

Cyan 15°, Magenta 75°, Yellow 0°, and Black 45°.

Printers use what is called, LPI or "lines per inch" do describe the halftone dot size. Generally between 120 -150lpi for normal paper, 765-85 for newsprint, and 175+ lpi for highquality on glossy stock. Basicly you need to scan at as ppi of less then the lpi to eliminate the dot on the scan. or choose to scan holding the dot where by you should try 2-3 times the lpi. ( I can rember the proper value)

Some scanners have a descreen function, my scanner it is hidden under an extended menu. Check your software.

The method I use for morie' removal in textiles or prescreened originals is:

Scanning at 4 times the resolution, switch to LAB mode, there slightly blur the a & b channels and run noise-->median on the lightness channel and then scale down to your desired image size. Then apply a slight usm to the lightness channel. Thou this may bring the pattern back so take care. Then switch back to RGB or CYMK.

Resizing steps also helps, forces photoshop to interpolate the colors more then once. Adding slight noise or blurs between moves also may help. This will degrade and or soften the image but the results are often better then a morie'.

jstaurtj



[This message has been edited by jstuartj (edited 09-14-2002).]

Added to FAQ. This had been answered some time back but I couldn't find the thread so this one's here to stay.
http://faq.ozoneasylum.com/FaqWiki/shownode.php?id=783&sortby=rating

Emps: I screwed up. I've double posted this in the faq's....and can't figure out how to delete the 'subtopic' I added to the page. I then added it, where I think it belongs, in 2D graphics/General 2D Graphics...

Sorry 'bout that.

NJ: Good idea making this a FAQ. No problem on the hiccup front . The actual FAQ is here:
http://faq.ozoneasylum.com/783/

I've tweaked it and added a few links and stuff.

Technically we can't delete FAQs until they have been voted down so if people could vote this out that would be cool:
http://faq.ozoneasylum.com/782/

For future reference we can move FAQs to their right place if you drop a note in here:
http://faq.ozoneasylum.com/220/

and rename it if you drop it in:
http://faq.ozoneasylum.com/346/

___________________
Emps

FAQs: Emperor

Now for the science bit :

From Larousse's (1995) 'Dictionary of Science and Technology':

quote:

---

moiré pattern (Comp, Print) A regular patterened effect formed by superimposing two or more sets of lines or dots of different pitch, or at certain angles; a defect to be avoided, esp. in half-tone reproduction and in half-tone four-colour process work. In computer graphics it occurs when a half-tone image is scanned using half-tone format or when such an image is scaled (changed in size) in an application program after it is scanned.

---

___________________
Emps

FAQs: Emperor

Yes. Actually, guys, I don't see moire here. I can see the problem that the resolution of the image isn't as high as the resolution you scanned at, but moire is caused when the two resolutions conflict and *cause a pattern*. There's no pattern here. Thankfully. This can be worked with; moire usually can't.

Usually Moire refers to the funky spirograph-line pattern you get when you take a repeating pattern and scale it (there are other causes, but that's the most common one I can think of). What you're seeing in that scan is just the half tone patter itself.. the actual dots. It's not really causing so much of a moire as it's causing noise. If you can see the half tone pattern, then you are already at a higher resolution than the lpi of the original print, so you should be fine by simply median blurring the image to knock out the dots and flatten the color (in this instance).


Whatever doesn't kill us...
Is probably circling back for another try.