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Descreening in Photoshop

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Descreening in Photoshop

Postby ZincRider » Fri Jan 22, 2016 8:14 pm

If you're a Photoshop user and scanning your own images, make sure you try the Sattva Descreen plugin. I bought it a couple of months ago and it still blows me away every time I use it.

It measures the screen pattern and performs a fully automated fourier based descreening process.
If you've ever tried fourier descreening manually, you know what a long and painful process it can be and how it can produce annoying artefacts. With this plug in you just push a button and it's done in a matter of seconds without any further ado. As simple as that. And the results are spectacular. No artefacts, no patterns that are part of the image getting in the way and messing everything up, no excessive blurryness. It usually does a much better job than I could do manually (and I was getting pretty good at this).

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 minium. Lower than that and you're starting to get moire patterns. 600dpi scans will be sufficient in most cases.

If you're trying to descreen images found on the web, you're probably out of luck. While it may be possible to fix moire patterns in lower res scans using fourier descreening, this plug in is not designed to do it.

The home edition is only €11.25. Well worth the money, considering how much time and effort it can save you.
There's a free demo that works for images up to 2000x2000px - too small for a cover at 600dpi, but enough to see what it can do.

This may sound like a sales pitch, but I really can't recommend it enough. :D
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Re: Descreening in Photoshop

Postby MrTinkertrain » Sun Feb 28, 2016 8:27 pm

I'll second that..
I've purchased the filter a few weeks ago and it does a damn good job.
Like ZincRider said, it won't work on pics with resolutions less than 600 dpi, but on 600 dpi scans it works like a charm
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Re: Descreening in Photoshop

Postby ZincRider » Tue Mar 01, 2016 8:44 pm

Ha! I knew I saw a couple of suspiciously nice CD covers from you.. :)
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Re: Descreening in Photoshop

Postby MrTinkertrain » Tue Mar 01, 2016 9:44 pm

Wow, thanks for the compliment :D
I've been looking for tools to get rid of those annoying moire patterns and I was thinking about getting the Sattva descreen plugin.
Your post about it pushed me over the edge so to say ;)
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Re: Descreening in Photoshop

Postby akovia » Tue Mar 08, 2016 11:11 pm

Ok,
I'd like to see if either of you can run your filter on this image. I'd like to check the results against doing it manually in gimp. If it's that much better, I'm going to solicit the gimp forums for a plugin upgrade. ;)

https://fanart.tv/wp-content/uploads/20 ... -Moire.jpg
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Re: Descreening in Photoshop

Postby ZincRider » Wed Mar 09, 2016 2:39 am

Not a chance, sorry. This is way past anything that this plugin could fix. Even manual descreening doesn't get me any acceptable results.

How on earth did this image get so bad in the first place? I've spent the last 30 minutes trying to make a scan a bad as that with no luck.
Could be a scaling problem. Maybe someone shrunk it without using any interpolation. Sure would mess up the screen pattern badly...
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Re: Descreening in Photoshop

Postby leepenny » Wed Mar 09, 2016 11:51 am

Image

best I could do i'm afraid - that was some crappy small scan with some horrid moire - probably not as good as you want - but maybe a bit better than what it was - (not using the above filter btw)
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Re: Descreening in Photoshop

Postby akovia » Wed Mar 09, 2016 1:05 pm

ZincRider wrote:Not a chance, sorry. This is way past anything that this plugin could fix. Even manual descreening doesn't get me any acceptable results.

How on earth did this image get so bad in the first place? I've spent the last 30 minutes trying to make a scan a bad as that with no luck.
Could be a scaling problem. Maybe someone shrunk it without using any interpolation. Sure would mess up the screen pattern badly...

Well this was a hopeful image, but I'm still interested in seeing what it does on something like this compared to my own manual results. That way I know if I'm missing out on something and can get people smarter than me to *hopefully* make a better automated plugin than what we have now.
The best way to motivate gimp developers is to tell them that Photoshop "does it better". Especially since gimp had it first. ;P

leepenny wrote:best I could do i'm afraid - that was some crappy small scan with some horrid moire - probably not as good as you want - but maybe a bit better than what it was - (not using the above filter btw)

Thanks lee. I was really just interested in seeing this plugin in action since it seemed to have a wow factor. Of course I wanted to test it with something hard. :)
This is what I got with a manual FFT.
https://fanart.tv/wp-content/uploads/20 ... Moire2.jpg
and after further processing.
Scrapped Princess-Moire3.jpg
Scrapped Princess-Moire3.jpg (420.93 KiB) Viewed 12886 times
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Re: Descreening in Photoshop

Postby ZincRider » Wed Mar 09, 2016 3:37 pm

akovia wrote:
ZincRider wrote:Not a chance, sorry. This is way past anything that this plugin could fix. Even manual descreening doesn't get me any acceptable results.

How on earth did this image get so bad in the first place? I've spent the last 30 minutes trying to make a scan a bad as that with no luck.
Could be a scaling problem. Maybe someone shrunk it without using any interpolation. Sure would mess up the screen pattern badly...

Well this was a hopeful image, but I'm still interested in seeing what it does on something like this compared to my own manual results. That way I know if I'm missing out on something and can get people smarter than me to *hopefully* make a better automated plugin than what we have now.
The best way to motivate gimp developers is to tell them that Photoshop "does it better". Especially since gimp had it first. ;P


Sometimes I do get pretty good results from images that are too small. Unfortunately this one just turns into a blurry mess. :( https://picload.org/image/wipwlll/scrap ... reened.jpg

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.

Did Gimp really have fourier descreening first? There have been FFT plugins for Photoshop for ages and I found references to the Sattva plugin dating back to 2004.

akovia wrote:and after further processing.
Scrapped Princess-Moire3.jpg


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..
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Re: Descreening in Photoshop

Postby akovia » Wed Mar 09, 2016 4:36 pm

ZincRider wrote:Sometimes I do get pretty good results from images that are too small. Unfortunately this one just turns into a blurry mess. :( https://picload.org/image/wipwlll/scrap ... reened.jpg

This isn't too far off from my results which is what I needed to know. If it was extremely better I would go raise a fuss in the gimp forums to improve what we have.
Thanks for testing it for me, but I kinda hoped it would be better so I could have something to look forward to.

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. :(

ZincRider wrote:Did Gimp really have fourier descreening first? There have been FFT plugins for Photoshop for ages and I found references to the Sattva plugin dating back to 2004.
http://photo.net/bboard/q-and-a-fetch-m ... 7&start=10

Yeah I'm pretty sure. I can't find the reference again when I first found out, but here is a reference from 2001.
http://photo.net/bboard/q-and-a-fetch-m ... 7&start=10
A little further searching and you can trace the gfourier plugin back to 1998. ver 0.1.1
https://marc.info/?l=gimp-announce&r=1&b=199807&w=1

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.
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