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Descreening in Photoshop

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Re: Descreening in Photoshop

Postby ZincRider » Wed Mar 09, 2016 7:45 pm

akovia wrote:
ZincRider wrote:The plugin is not designed to fix moiré patterns. It prevents them before they can happen. It will turn this https://picload.org/image/wipwlgo/original.jpg into that https://picload.org/image/wipwlgc/descreened.jpg in a matter of seconds.

Not sure what you mean by before they happen, but that is indeed moire. I believe that is halftone moire specifically, which gimp handles also just fine. Unfortunately it takes 20 times as long as your plugin. :(


Sorry, my bad. Of course the screen pattern forms moiré patterns as well, but the plugin will fix them as they're part of them screen pattern. Other patterns that are part of the image are not affected.

It won't fix the moiré patterns that occur when you shrink an image with a screen pattern or scan it with too little resolution. Like this one: https://picload.org/image/wiwdrlo/moire2.jpg (side note: I had to use nearest neighbour interpolation to produce the pattern. Bicubic would have smoothed it out so much, there would hardly be any moire left)

akovia wrote:
ZincRider wrote:I notice both of you really crushed the shadows, which increases the contrast and makes the colors pop, but unfortunately it eliminates the difference in color between the dark fabrics and darker shadows..

Yes of course. When dealing with a picture this bad you don't have a lot of options and crushing the blacks hides a LOT of problems. If you have a better solution I'm all ears.


Crushing shadows and highlights sure can fix some problems, but I didn't see anything in your image that would have called for it. If it weren't for the horrible moiré (which you were able to smooth out nicely) and the clipped highlights, I wouldn't consider it a bad picture at all.
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Re: Descreening in Photoshop

Postby MrTinkertrain » Thu Mar 17, 2016 10:58 pm

After using the Home Edition of the Descreen plugin for a few weeks I've been pretty content and sometimes amazed by the results it produced.
There is also a Professional Edition of the plugin available with more options , and tonight I decided to purchase this Professional Edition :)

After reading the comments on the picture akovia posted, it didn't make any sense to me to give it a go myself with the Home Edition.
The Professional Edition has got some more options, so I will try to see if that one can do something more on this picture as the Home Edition.
And if I'm able to make some sensible comments on that I'll post them here ;)
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Re: Descreening in Photoshop

Postby ZincRider » Mon Mar 21, 2016 2:53 am

So how is it? While it does give you more control over every parameter, most of the professional edition sample pics on the website don't look all that much better than what can be achieved with the home edition.
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Re: Descreening in Photoshop

Postby MrTinkertrain » Mon Mar 21, 2016 8:33 am

I have to say that I haven't done to many covers since I bought it and I'm thinking that the Home Edition should do just fine when it comes to producing "fanart.tv-material".

But I'm in the process of doing a study to see if I could start up a business of my own in which photo restauration and retouching are some of the services I would offer.
And at the moment a temporary discount is being offered on the plugin, so I thought this might be a good time to upgrade to the Professional version ;)

But once again, I think that the Home Edition of the plugin will work just fine
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Re: Descreening in Photoshop

Postby ZincRider » Mon Mar 21, 2016 2:30 pm

Yeah, it's perfectly fine for me. I rarely have to redo anything manually and when I do, it's an easy fix.
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Re: Descreening in Photoshop

Postby j7n » Tue Nov 15, 2016 6:09 am

Sattva Descreen is the next best thing since sliced bread! I like how after processing the image remains natural, and not "plastic" or with a new texture, which manual methods using median, etc., would yield. With default sharpness there is no ringing.

" In order to measure the screen pattern, the plug in needs a scan of high enough resolution. Screen frequency multiplied by three is the absolute minimum. "

I have obtained satisfactory results with resolution significantly lower than this. The limit for a 150 lpi screen is about 310 dpi, or 600 dpi on a source with chroma subsampling (unfortunately they are common). Smaller images can still be somewhat improved. The image must be upsampled to a suitable dpi first, and then usually the screen angles should be input by hand if the definition is so low that the color dots cannot be resolved and measured. Usually Descreen can measure the angle of Black, and the others can be guessed (such as 15,75,45). If it consistently reports 37 on one color or another, the then angles are likely 7,67,37,(83). Sometimes even the screen frequency must be guessed. Decreening must be the first step in processing, before Rotation; in case of a rotated image the angles will be odd.

My technical knowledge is sketchy here, but I suspect that this works because the moire of a color print has a lower frequency than the screens that generated it. And if the image were to be filtered so that the moire is removed, then frequencies (image detail) between it and the screen would be wiped as well.

The enemy of Descreen is vector text that breaks the pattern. I found that a good compromise is to filter an image with text on another layer without applying moire reduction (only lowpass), then afterwards select the text and use moire on photographic parts only. Audio Fidelity covers are rare example where all artwork is printed as raster with halftones (at a higher frequency ~200 lpi), and these covers are always processed perfectly without any lost sharpness on text.

Some examples with Sattva Version 3.5, and less than ideal sources. Some show fine raster text on reproductions.

backbeats - Before - After

krall - Before - After

suzi - Before - After
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Re: Descreening in Photoshop

Postby ZincRider » Thu Nov 17, 2016 12:14 am

I've had some luck descreening a couple of images of insufficient resolution, but it was hit and miss - mostly miss. But that's because the images were badly messed up before I even touched them.

I wouldn't consider the Suzi Quatro image a bad scan. The screen pattern is large and clear - easy fix and the result speaks for itself. The others came out surprisingly good looking, but there still might be some room for improvement. I can get the Krall image much smoother with manual FFT descreening, but only with excessive ringing...
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Re: Descreening in Photoshop

Postby j7n » Thu Nov 17, 2016 4:38 pm

Cleanup of Blue (Y angle) worked surprisingly well in "backbeats". Usually it doesn't work. The dpi was 400 (2.3x).

Color is wiped out in suzi. Surprisingly the program doesn't need good color quality to perform actual reduction in red-green, only to do the intial measurement. (That is for the older version.) I had a few oversharpened pictures, where the dots were clipped white, but removal of the rosette pattern still mostly worked.
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Re: Descreening in Photoshop

Postby ZincRider » Thu Nov 17, 2016 8:15 pm

j7n wrote:Cleanup of Blue (Y angle) worked surprisingly well in "backbeats". Usually it doesn't work. The dpi was 400 (2.3x).

Color is wiped out in suzi. Surprisingly the program doesn't need good color quality to perform actual reduction in red-green, only to do the intial measurement. (That is for the older version.) I had a few oversharpened pictures, where the dots were clipped white, but removal of the rosette pattern still mostly worked.


The colors don't look so bad to me. There's a little clipping, but I guess that might be caused by the physical limitations of the scanner used.
The print on the back of the page shining through can be annoying to fix sometimes.

Sharpening can bring out problems from what I've seen so far.

Scanning CD covers certainly feels like going the easy way to me. The plugin works so well with so little effort with decent scans, it's ususally worth making a new one that doesn't suffer from all the issues instead of working with someone else's questionable scan.
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Re: Descreening in Photoshop

Postby ZincRider » Sat Jun 03, 2017 9:37 pm

MrTinkertrain wrote:I have to say that I haven't done to many covers since I bought it and I'm thinking that the Home Edition should do just fine when it comes to producing "fanart.tv-material".

But I'm in the process of doing a study to see if I could start up a business of my own in which photo restauration and retouching are some of the services I would offer.
And at the moment a temporary discount is being offered on the plugin, so I thought this might be a good time to upgrade to the Professional version ;)

But once again, I think that the Home Edition of the plugin will work just fine


I'm using the professional edition now as well and it's really good.

It has more severe modes of moire elimination for images that the home edition just won't smooth out properly. In the past I sometimes had to use an FFT plugin to manually remove the remaining moire (which was trivial after the Sattva-plugin had done its magic). Now I use this instead.
The developer recommends duplicating the scan layer and descreening one layer using the regular mode and the other one using the more severe one. The one with the more severe descreening can then be applied to the regular one using a layer mask. Interestingly that's just how I was working with the FFT plugin.

Another feature that I'll probably use a lot is the noise reduction. It does a great job at removing the noise that is left after descreening while leaving image detail intact. Just what I needed. It's the right tool for the job.

I haven't felt the need to mess with individual screen angles yet, but I guess it will come in handy sooner or later.

The professional edition is quite a bit pricier than the home edition, but it's aimed at pros who earn their money using it. If you're descreening a lot and feel you need the additional features you can still get your money's worth out of it even as a non professional.
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