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Microstock Photography Forum - General => Software => Photoshop Discussion => Topic started by: RacePhoto on February 16, 2013, 09:58

Title: De-Screen option in Photoshop or Elements?
Post by: RacePhoto on February 16, 2013, 09:58

If I scan the print at 2400 (right) I get screen artifacts. If I add de-screen the software says, I need to reduce the resolution to 600 dpi, which then gives me a 3.2MP image. I want larger.

Is there a way to scan at 2400 and de-screen afterwards? Filter, plugins, is it a feature I'm just missing?

(http://s5.postimage.org/jhj4o9enb/steam_loco_screen_web.jpg) (http://postimage.org/)
both reduced to 1000 pixels high (http://postimage.org/)

Title: Re: De-Screen option in Photoshop or Elements?
Post by: dk on February 16, 2013, 11:58

In photoshop under the noise filter there's an option called despeckle, i think it's similar to descreen.

Title: Re: De-Screen option in Photoshop or Elements?
Post by: Jo Ann Snover on February 16, 2013, 15:05

What you need is a FFT plugin (Fast Fourier Transform). There is one but not for 64 bit for Mac - I think they updated it for Windows 64 bit, but as I don't use that I'm not sure

http://www.3d4x.ch/Swift's-Reality/FFT-Photoshop-plugin-by-Alex-Chirokov/16,35 (http://www.3d4x.ch/Swift's-Reality/FFT-Photoshop-plugin-by-Alex-Chirokov/16,35)

There are some other Java based ones - I did use to remove a bobble pattern on a scan on an old print and it works great (if with a primitive UI)

Title: Re: De-Screen option in Photoshop or Elements?
Post by: RacePhoto on February 16, 2013, 23:03

Thanks both. I found Despeckle (don't understand it), found tutorials saying Gausian Blur or Median filter, then Unsharpen. Some filters and plugins, for sale. Convert to LAB and edit A and B channels. I was totally confused. (shh, I think I still am.) I'll try the link!

Quote from: jsnover on February 16, 2013, 15:05

What you need is a FFT plugin (Fast Fourier Transform). There is one but not for 64 bit for Mac - I think they updated it for Windows 64 bit, but as I don't use that I'm not sure

[url]http://www.3d4x.ch/Swift's-Reality/FFT-Photoshop-plugin-by-Alex-Chirokov/16,35[/url] ([url]http://www.3d4x.ch/Swift's-Reality/FFT-Photoshop-plugin-by-Alex-Chirokov/16,35[/url])

There are some other Java based ones - I did use to remove a bobble pattern on a scan on an old print and it works great (if with a primitive UI)

Title: Re: De-Screen option in Photoshop or Elements?
Post by: Beppe Grillo on May 09, 2013, 12:54

The Lab (not LAB) method is the one use for years by most of the pros of pre press.

Convert the image to Lab
1) use gaussian blur or median (in very subtle quantity) on the a and b channels (generally they contain most of the color noise)
2) if necessary use despeckle on the L channel too