"Chicken skin" effect when scanning b/w images

Archived from groups: rec.photo.digital (More info?)

Contact the person or business that holds the copyright to the image and
purchase reproduction rights from them.

KB




"jersie0" <notreal@aol.com> wrote in message
news:h9nf0110v4vm6p8b15003act80kqrfimdh@4ax.com...
>I have an ancient cheap Acer scanner that works just fine for me the
> few times I need it.
>
> The one thing it does miserably though is scanning black and white
> photos out of books. I've tried scanning pictures from old high
> school yearbooks, or pictures out of books so my kids can use them in
> history reports, and here's what happens:
>
> I get an image with a pattern of dots visible all over the darker
> portions. It looks like there was a net draped over the image. Or it
> looks like the image has goosebumps. I'll call it the "chicken skin
> effect" because the evenly-spaced translucent dots look like the
> surface of skin from uncooked poultry.
>
> Is there some special technique I'm supposed to be using when scanning
> black and white photos (any photos maybe) from books? Mind you, my
> scanner's not great, but text comes out fine, color or black and white
> standalone photos come out great, it's only when scanning from a book
> that I get this phenomenon.
>
> Yes, as best I can, I press down on the scanner cover while the scan
> is occurring. I've even left the cover up and pressed down on the
> book hard enough that the page is clearly hard up against the glass.
>
> This one is driving me nuts. Anyone else ever see it? And what's the
> answer?

Archived from groups: rec.photo.digital (More info?)

jersie0 wrote:
> I have an ancient cheap Acer scanner that works just fine for me the
> few times I need it.
>
> The one thing it does miserably though is scanning black and white
> photos out of books. I've tried scanning pictures from old high
> school yearbooks, or pictures out of books so my kids can use them in
> history reports, and here's what happens:
>
> I get an image with a pattern of dots visible all over the darker
> portions. It looks like there was a net draped over the image. Or it
> looks like the image has goosebumps. I'll call it the "chicken skin
> effect" because the evenly-spaced translucent dots look like the
> surface of skin from uncooked poultry.
>
> Is there some special technique I'm supposed to be using when scanning
> black and white photos (any photos maybe) from books? Mind you, my
> scanner's not great, but text comes out fine, color or black and white
> standalone photos come out great, it's only when scanning from a book
> that I get this phenomenon.
>
> Yes, as best I can, I press down on the scanner cover while the scan
> is occurring. I've even left the cover up and pressed down on the
> book hard enough that the page is clearly hard up against the glass.
>
> This one is driving me nuts. Anyone else ever see it? And what's the
> answer?

You get the "dotted" scanned image because the original image is dotted.
You are not scanning a continuous tone B/W photo. You are scanning a low
resolution, printed image. It is composed of many fine discrete dots.
Your scanner SHOULD have a setting for scanning images printed from
Newspapers, Magazines, Fine Art Prints, etc.
In your case, you should select the setting for newspapers.
It won't "Cure" the problem but it will help a lot.
Bob Williams

Archived from groups: rec.photo.digital (More info?)

chrlz@go.com wrote:
> Or to summarise, if the scanner doesn't have a descreen or demoire
> function built-in, just:
>
> 1. Scan at about twice the resolution you need.
> 2. Use an image editor or browser to blur the image (experiment to work
> out how much)
> 3. Resample the image down to the size you need. (if the editor has
> different resizing algorithms, you may need to experiment again to find
> the best result)
>
> The moire pattern should be reduced or eliminated.

Hi...

I agree... and add that a carefully chosen degree of
edge preserving smooth will help, too.

Ken

Archived from groups: rec.photo.digital (More info?)

On Wed, 09 Feb 2005 15:28:02 +1300, Bartshumandad
<bartshumandad@netscape.net> wrote:

>
>
>Ken Weitzel wrote:
>>
>>
>> chrlz@go.com wrote:
>>
>>> Or to summarise, if the scanner doesn't have a descreen or demoire
>>> function built-in, just:
>>>
>>> 1. Scan at about twice the resolution you need.
>>> 2. Use an image editor or browser to blur the image (experiment to work
>>> out how much)
>>> 3. Resample the image down to the size you need. (if the editor has
>>> different resizing algorithms, you may need to experiment again to find
>>> the best result)
>>>
>>> The moire pattern should be reduced or eliminated.
>>
>>
>> Hi...
>>
>> I agree... and add that a carefully chosen degree of
>> edge preserving smooth will help, too.
>>
>> Ken
>>
>>
>The Median filter can be useful too, but again you may need to sharpen
>your edges afterwards.

Sometimes rotating the original anywhere between 5 & 45 degrees
(experiment) on the scanner bed can help the above filters work
better.

--
Owamanga!

Archived from groups: rec.photo.digital (More info?)

jersie0 wrote:
> Wanted to thank everyone for the great suggestions. Yeah, the Morais
> (spelling?) issue was what I was dealing with, and all the tips here
> helped.

mmwah-ray (Dinah Shore syndrome)

moiré