Descreening scanned photos

[leapyear]

Is there a way to descreen a photoshop image?
The client failed to do this when scanning in artwork originally
printed in a book.

Thanks-

[Ramón_G_Castañeda]

Illegal use of copyrighted art aside, any workaround is going to leave you with a smudged issue that looks like ...

[Abuse removed by moderator]

[ted939]

Why would you bring up unmentioned illegal uses? If you're going to bring up illegal use of copyrighted art, then why not bring up illegal use of counterfeit money, stolen equipment or forced labor?

Please, everybody, keep all parts of answers relevant to the question/topic.

[c.pfaffenbichler]

Why would you reply to a post from 2008? 

[Guest]

Any scan needs to be done at high rez 600ppi or more and angled so you lose as much of the moire as possible

[p_taz]

Scan at 600-800 angled as per Buko's advice and then median filter at 2.....
Then if it looks soft, use the high pass/hard light sharpening method.

[leapyear]

Thanks for all the advice. I'll give rescan a shot. It's not illegal use.

[Steve Fairbairn]

Many scanners have a de-screen thing. And on some you can specify the screen density that you want to de-screen. Use it if you can.

The scanned image will always be a bit softer than the original but at least you get rid of moirés which can be a B*** to edit afterwards.

If you can get hold of one, it's a good idea to use a screen measuring film with convergent lines so that you can see exactly what the screen density of the printed original is. That way your scanner de-screening value won't be hit-and-miss. You may be able to get hold of such a film from a print shop although they're a bit difficult to find these days.

Failing that, you can scan in HiRes like Buko says. Try converting the image to Lab colour and then blurring each of the 3 channels individually; more for the colour channels than for the greyscale channel or until you just can't see the dots.

[p_taz]

Steve, have a try of the method in #3, easier and better result. I gave up blurring years ago as a bad joke. Usually, I measure the screen ruling and use the scanner descreening first, but the median method is much better IMHO.
and.... if you dont already, try the high pass/hard light sharpening method...amazing results in many cases.

[Lundberg02]

I've ALWAYS had good luck with the 15 deg rotate.

[Guest]

>I've ALWAYS had good luck with the 15 deg rotate.

Thats not always practical though. What if you are scanning a whole page and you don't have room to rotate? High rez scan is the best way to help eliminate moiré. Another way is to scan at odd screen rez like 500ppi, 700 or 800ppi.

Now you have the high rez scan if you run a small amount of median you can down sample the image to 300ppi this will also help reduce the moiré.

[Lundberg02]

i can turn my scanner 15 deg without any problem. What? Oh.

[HarleyTDavis]

I know this is old, about as old as my scanner.  A canon mg6300 all in one.  I've used epson scanners in the past, canon as well.  I stayed with canon for the printing.   Just better use of ink and you can even fill your own to make your own color balance.

If you are scanning and using the 12.7 to 20 degree angle method, if you have a full page to scan, start with the top two thirds, then do the bottom two thirds, etc.  Even in 2008 there were programs to stitch these kinds of images together.  Now photoshop can do it for you.  Make sure you turn on the scanner descreen algorithm.  After this, you can desaturate the image until the color lines are almost in-distinguishable, but I would do this on it's own layer, because we'll be applying it as an effect over the top.  Next, you'll snapshot how the image looks with this as an effect either as an overlay or as a luminosity\hue\sat\color blend.  Now this image is your overlay on top of the old; it will be slightly less effective than the previous, which is okay.  Now go into it's colors and blur them slightly, this will be placed over your original image, giving you more solid color tone, but a little washed out.  Snapshot again, and paint on some blur in different colored areas.  Now apply a saturate filter to bring up the saturation of color, maybe how vivid they are... ...and finally give it a sharpen filter.  Snapshot this, and overlay on top of the original image as a color blend.  At this point, you'll still see slight variations in some areas.  They are easily removed with the blur or blend brush, use color as the mode.

This yields very decent results.  I've done really old color photos this way and preserved much of the color balance of the photo from the type of film used.  It keeps the look and feel, while gaining some sharpness, but preserves the memory just fine.

With magazine or article from another publication, you may lose a little definition, but you can redraft some of that.  I use the edging method that turns the edges into something like a pencil drawing, then darken that and overlay it as a luminosity adjustment, darkening the image at the edges or providing a shading where the details appear.  This almost recovers the detail.  But the caveat is that I have to opperate this method separate from the rest, by starting with the original image, copying the layer, inverting the copy, setting to a dodge-type blend mode, then bluring it just right, snapshoting, desaturating it just right, and then darkening the edge and lightening the middle or bright tonal areas that are left.  Details in the midtones should still be a middle grey, but edges should be black.  Take a snapshot of this, and overlay that as a luminosity or multiply blend mode, then adjust opacity to taste.  Luminosity usually works a little better, as it doesn't end up looking like a comic book over-draw.  You can also create a copy of the original layer, add a mask, and after using the black and white edging to select only nonwhite (Not a racist), then filling only those areas; after this, you can add noise so that these areas have some definition and realism.

If you do this right, you could put the main or closest focal areas in the best sharpness by darkening them the most in the edges layer (darken all of the edge and detail fully first and then brighten the rest in increments), then the other areas should lighten out toward middle grey for farther edges or detail, and white for middle tone areas.  This will give you a focal area that's nice and sharp, and other areas that are sharp but draw you into the focus area.  I've had this come out just a little "creepy" because people tend to look very powerful, almost real, and there's a feeling of dimension to them that makes the image seem almost alive, which creeps some people out, especially in the wake of watching demonic-possession horror films.

[Ramón_G_Castañeda]

A lower-case i at the very beginning of a line and followed by a space will give you italics.

[Lundberg02]

That ain't what happened.

[p_taz]

you forgot to leave a
i space after the i

[Stephen_A_Marsh]

You can try:

https://ft.rognemedia.no/

or

https://fixelalgorithms.co/products/fftwizard2/