Reduce Halftone Effects of Scanned Image

I have scanned several images for a project which are poor quality halftoned. I'm only about 2 weeks into Photoshop but I have yet to find a way to clean them up satisfactorily. I have scanned the images using the descreen option but that was of little help.

I'd appreciate any suggestions from someone with more skill than I have.

Thanks.

Jim

Hi Jim

I've had good results using Filter:Noise:Dust & Scratches and Filter:Noise:Median. Play with the sliders.

Stan

Hint 1:
Search the archives ... this has been extensively discussed, with many recommendations and procedures.

Hint 2:
If you *really* want to go into this problem, see

http://www.reindeergraphics.com/index.shtml

Specific to removing halftone screening would be "The Image Processing and Measurement Cookbook" at
http://www.reindeergraphics.com/tutorial/index.shtml

The entries most applicable would be
http://www.reindeergraphics.com/tutorial/chap4/fourier01.htm l
and
http://www.reindeergraphics.com/tutorial/chap4/fourier13.htm l

"Jim Marhoefer" wrote in message

I have scanned several images for a project which are poor

quality

halftoned. I'm only about 2 weeks into Photoshop but I

have yet to find a

way to clean them up satisfactorily. I have scanned the

images using the

descreen option but that was of little help.

I'd appreciate any suggestions from someone with more

skill than I have.

Thanks.

Jim

I have scanned several images for a project which are poor quality halftoned.

What do you plan to do with them? Print them on a press? Print them on a home consumer-grade printer? Put them on the Web?

--
Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

Tacit,

Actually the pics are for my wife's H.S. reunion and they want photos displayed of their deceased classmates. The only source I have is their annual. I am also making up their badges but the images are small enough that quality is not a factor.

Thanks for the reply.

Jim

"Tacit" wrote in message

I have scanned several images for a project which are poor quality halftoned.

What do you plan to do with them? Print them on a press? Print them on a

home

consumer-grade printer? Put them on the Web?

--
Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

Actually the pics are for my wife's H.S. reunion and they want photos displayed of their deceased classmates.

So the pictures are going to be enlarged, and used to make signs or other displays?

It's virtually impossible to enlarge a halftoned picture without the picture completely falling apart. I doubt you're going to get decent quality; sorry...

--
Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html

I have some time. Send me an image and I will see what I can do with it.

take out the spam

Tacit wrote:

Actually the pics are for my wife's H.S. reunion and they want photos displayed of their deceased classmates.

So the pictures are going to be enlarged, and used to make signs or other displays?

It's virtually impossible to enlarge a halftoned picture without the picture completely falling apart. I doubt you're going to get decent quality; sorry...

In article <KLVad.2343$>,
"Jim Marhoefer" wrote:

I have scanned several images for a project which are poor quality halftoned. I'm only about 2 weeks into Photoshop but I have yet to find a way to clean them up satisfactorily. I have scanned the images using the descreen option but that was of little help.

One trick that sometimes helps -- depending on the screen ruling, scanner resolution and wind direction ;) -- is to scan the printed originals slightly crooked, say three to five degrees out of square, then orient them correctly by rotating in Photoshop. Changing the scan resolution by a small amount can help as well -- and don't use a resolution any higher than necessary to avoid pixelation. These effects are rather unpredictable, so be prepared to do some experimenting ...

Rotating will soften the images a bit, but ultimately you can't expect to completely eliminate moiré while preserving all the sharpness of the original. Sometimes I get nostalgic for obsolete analogue methods: years ago we could usually produce very nice rescreens, just barely blurred by holding a piece of ordinary plate glass between the copyboard and the lens of our old horizontal camera, and gently waving or rotating it back and forth during the main exposure.

--
Odysseus

Jim

You can not attach files sent to the news group. You will have to e-mail directly to me at the address I gave.

dp

Jim Marhoefer wrote:

Bogus,

Attached is one of the poorer pictures I'm trying to correct. I really appreciate your help. Thanks.

- Use BW setting when scanning
- open picture, duplicate, eventually extract subject
- apply poster edges (find settings) OR find contour OR stamp to the duplicate
- lower fill, % setting may vary widely.

"Jim Marhoefer" a

Odysseus wrote:

<snip>
....but ultimately you can't expect

to completely eliminate moiré while preserving all the sharpness of the

original.

Not true, actually. See
http://www.reindeergraphics.com/tutorial/chap4/fourier13.htm l

Bogus,

I sent the pic via email but the email was returned as undeliverable.

--

Jim Marhoefer

"bogus" wrote in message

I have some time. Send me an image and I will see what I can do with it.

take out the spam

Tacit wrote:

Actually the pics are for my wife's H.S. reunion and they want photos displayed of their deceased classmates.

So the pictures are going to be enlarged, and used to make signs or

other

displays?

It's virtually impossible to enlarge a halftoned picture without the

picture

completely falling apart. I doubt you're going to get decent quality;

sorry...

(DrJohnRuss) wrote in message news:...

Odysseus wrote:

<snip>
...but ultimately you can't expect

to completely eliminate moiré while preserving all the sharpness of the

original.

Not true, actually. See
http://www.reindeergraphics.com/tutorial/chap4/fourier13.htm l

The holes for suppressing the periodical spikes in the spectrum by a mask are FAR too small.
Because of leakage the influence (area) of the spikes is much larger. Therefore it´s necessary to apply additionally an ordinary low pass filter (here a Butterworth filter) to remove the remaining patterns. The final result would not be much different if we used only the low pass filter without the mask.
Some demonstrations are here (maybe 600kBytes):
http://www.fho-emden.de/~hoffmann/fft31052003.pdf

It´s therefore not correct to promise "sharpness of the original".

The readers in this forum are probably not interested in a scientific dispute, therefore I´ll leave it at that.

A practical and cheap alternative is "synchronous scanning": http://www.fho-emden.de/~hoffmann/scan121200.pdf

Best regards --Gernot Hoffmann

Gernot,

Thank you for the reply. I tried the fho-emden websites you referenced but didn't get far since I don't speak German. Are there any English translations?

Thanks again.

--

Jim Marhoefer

"Gernot Hoffmann" wrote in message

(DrJohnRuss) wrote in message

news:...

Odysseus wrote:

<snip>
...but ultimately you can't expect

to completely eliminate moir

(Gernot Hoffmann) wrote

<snip>
...but ultimately you can't expect

to completely eliminate moiré while preserving all the sharpness of the

original.

Not true, actually. See
http://www.reindeergraphics.com/tutorial/chap4/fourier13.htm l

The holes for suppressing the periodical spikes in the spectrum by a mask are FAR too small.
Because of leakage the influence (area) of the spikes is much larger. Therefore it´s necessary to apply additionally an ordinary low pass filter (here a Butterworth filter) to remove the remaining patterns. The final result would not be much different if we used only the low pass filter without the mask.

The size and shape of the holes used to suppress the spikes (and the important apodization of the edges) can be adjusted in the program, so differences of opinion about the proper size don't affect the general statement that the moire or halftone pattern can be removed. As in your demonstration, a low pass filter afterwards fills in empty gaps in the image. In any case, removing the periodic noise, of whatever source, allows the details actually present in the original image to be better seen.

The readers in this forum are probably not interested in a scientific dispute, therefore I´ll leave it at that.

Probably true, and in any case I don't think we have much to dispute. The underlying truth that I think we agree about is that processing such images in Fourier space is a valuable tool. With the plugins, such operations can be performed within Photoshop.

Hi Jim

I did some cleaning, and a 4x enlargement,
of pic072. The results, and the original,
can be seen here:

http://FreshArtDaily.com/tweaks/pic072_cleaned_comparison.jp g

http://FreshArtDaily.com/tweaks/pic072_cleaned_enlarged_comp arison.jpg

Technique:

I duped the original layer, then
used the Median and Dust and Scratches filters
on the dupes, played with the opacities
of each of those layers til I was pleased,
then added a Curves adj. layer on top,
then copied the whole sandwich, pasted
it on top, and unsharp-masked that a bit.

The result would be better with a higher-res
scan. But, given the lo-res of pic072.jpg, and
the source for the scan, this isn't too bad, I think.

Thus: scan the images at 600 ppi or more,
apply these techniques, and I think you're set.

Stan

"Jim Marhoefer" ...

Gernot,

Thank you for the reply. I tried the fho-emden websites you referenced but didn't get far since I don't speak German. Are there any English translations?

Thanks again.

Jim,

here is the list of all tutorials:
http://www.fho-emden.de/~hoffmann/howww41a.html

Nearly all are in "a kind of English".

Best regards --Gernot Hoffmann

(Gernot Hoffmann) wrote in message > here is the list of all tutorials:

http://www.fho-emden.de/~hoffmann/howww41a.html

WOW Gernot.... A great deal of documents which seem to be a real wealth of information. I have to say THANK YOU. I will try to download them all, and read them all.

Mohamed Al-Dabbagh
Senior Graphic Designer

Mohamed Al-Dabbagh wrote:

(Gernot Hoffmann) wrote in message > here is
the list of all tutorials:

http://www.fho-emden.de/~hoffmann/howww41a.html

WOW Gernot.... A great deal of documents which seem to be a real wealth of information. I have to say THANK YOU. I will try to download them all, and read them all.

I second Mohamed's recommendation. A lot of good material there for those who want to delve into details on a large number of imaging and Photoshop related subjects.
--

Mike Russell
www.curvemeister.com
www.geigy.2y.net

Stan,

Sorry I haven't gotten back to you sooner but had an extremely busy (plumbing(ugh)) weekend.

I checked out the pics and I must say they are far better than anything I have been able to do so far. That particular picture is the very worst one. I will definitely try scanning at a higher res and applying the effects you suggested.

Thanks again, Stan.

Jim Marhoefer

"Stanley Krute" wrote in message

Hi Jim

I did some cleaning, and a 4x enlargement,
of pic072. The results, and the original,
can be seen here:

http://FreshArtDaily.com/tweaks/pic072_cleaned_comparison.jp g
http://FreshArtDaily.com/tweaks/pic072_cleaned_enlarged_comp arison.jpg
Technique:

I duped the original layer, then
used the Median and Dust and Scratches filters
on the dupes, played with the opacities
of each of those layers til I was pleased,
then added a Curves adj. layer on top,
then copied the whole sandwich, pasted
it on top, and unsharp-masked that a bit.

The result would be better with a higher-res
scan. But, given the lo-res of pic072.jpg, and
the source for the scan, this isn't too bad, I think.

Thus: scan the images at 600 ppi or more,
apply these techniques, and I think you're set.

Stan