Photoshop function that eliminates pattern resulting from high-res scan

[huckbuc]

I scanned a photo from a book (the photo stretched over an entire page, about A4 in size), and I want to print it as a poster about 5 X 3 ft in size.

When I zoom in into the scanned photo, to see how it will look like enlarged, I see rather ugly marks, arranged in a pattern. See the attached photo. A friend told me that these marks result from the mesh used in the printing process of the book.

Is there a photoshop function that eliminates these marks? I know nothing about graphics or photoshop, but I guess there must be a function that replaces the value at each pixel with the average values of all pixels in a neighborhood around it, and thus smoothes the image and solves my problem.

Will appreciate any help!

 

[gedstar]

2 questions what resolution did you scan the photo at? can you post the actually scanned image

 

[Tom Mann]

Google {Fourier transform plugin photoshop remove pattern site: photoshopgurus.com}

Simple smoothing / blurring is not sufficiently selective. If you apply strong enough to get rid of the dots, it blurs important features too much. There are ways to use simple blurring multiple times each shifted by a small amount, and that is not too bad. That generally accepted method is the Fourier transform method, but it is a quite advanced technique.

HTH,

Tom M

 

[huckbuc]

2 questions what resolution did you scan the photo at? can you post the actually scanned image

The scan is about 10,000 X 14,000 pixels. I'd rather not post it in full because of copyright issues - the original photo is (sadly) not mine.

 

[Tom Mann]

I just re-read your original post and picked up on the fact that your original is only about the size of a piece of copier paper, ie, ~ 8.5" x 11.5". Even if there were no half-tone pattern, the resolution used to print the book is not even close to being adequate to have a sharp image when enlarged by 5x (ie, to 5' wide). The fact that you used a high ppi setting when you scanned it is helpful, but will not produce or improve detail that simply isn't present in the original.

My guess is that if you do nothing to the halftone pattern, most people viewing it will subconsciously catagorize it as a "blow-up" and accept it for what it is. I see this done often with photo-based advertisements (about 5' high) used in the windows of trendy clothing stores in malls.

Tom M

 

[huckbuc]

Thanks, Tom, for your reply. Of course it's impossible to keep the image sharp when enlarging it by a factor of 5 or so, but I was hoping to learn about a photoshop trick that will make the red part in the photo above more uniformly red, the black more uniformly black, etc. I just looked into the FFT plugin your advised me to check, and that seems to do the trick. Thanks again!

 

[Tom Mann]

Glad to have helped. If your search didn't happen to turn up this thread: https://www.photoshopgurus.com/foru...665-need-help-getting-rid-canvas-texture.html

you may want to have a look at it. That guy's problem was the texture of the canvas that his image was printed on, not a half-tone pattern, but the Fourier transform method works just as well for that.

If you are not comfortable with such techniques, another possibility is to use a scanner whose software includes a "de-screening" feature. These sort-kinda work, but never as well as applying the FT method manually. For example, different parts of an image may require different settings.

Good luck with your project,

Tom M

 

[huckbuc]

Thanks again, Tom, you are very helpful!