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Using the FFT filter to remove photgraphic paper texture

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  #11  
Old 06-24-2005, 02:14 PM
fat0n3s fat0n3s is offline
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Great tutorial ByRo!

Can FFT be used to remove noise as well, or just repeated texture?
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  #12  
Old 06-24-2005, 02:33 PM
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jcr6 jcr6 is offline
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Random Noise vs. Pattern Noise

We call that "repeated texture" of yours Pattern Noise.

You can implement a blur function, which is good at removing Random Noise with an FFT (including some filters that are much more interesting than a Gaussian Blur). That is pretty much the limit, however. There is no equivalent to a Median filter or the new Smart Blur in PSCS2.

So the answer is "Yes, but..."

...but they're not very useful except in specific cases.
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  #13  
Old 06-25-2005, 10:31 PM
SteveD SteveD is offline
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Having difficulty with IFFT

Hello -- I am somewhat a pretty novice user of Photoshop CS2 and am interested in the FFT tutorial.

I am having difficulty, however at step 6, the Inverse Fourier Transform. I took particulat note of step 6. When I do the inverse FFT I do not get a grey scale image, I get something like the FFT but colored, no image at all.

I must be missing something. Please help.

SteveD
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  #14  
Old 06-26-2005, 09:59 AM
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byRo byRo is offline
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Hi Steve, welcome to RetouchPRO

When you said step 6 inverse FFT, I think you meant step 7. Step 6 is just a reminder to turn the channels back on

If you are getting something coloured after the inverse FFT, then I say that you probably did the FFT again and not the IFFT. When things go wrong in the IFFT, you usually get a semi-transparent grey mess.
Try doing the FFT and then the IFFT immediately after, see if that works.

One thing that isn't (wasn't) in the tutorial is that before doing the IFFT the image must again be just one background layer.

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  #15  
Old 06-26-2005, 03:18 PM
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Cameraken Cameraken is offline
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I think I know what Steve is doing

6) Select all channels again
- On the channels palette turn back on the green and blue channel (easy to forget this bit);
- If necessary, flatten the layers (<Alt><L><F>);

It is not enough to simply have the “eye” on the RGB channel as in picture 1
You must have the RGB channel Highlighted as in picture 2

Ken
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  #16  
Old 06-26-2005, 03:24 PM
SteveD SteveD is offline
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Re: FFT filter implementation problems

Ro,

Thank you for responding so quickly.

I did as you suggested doing an FFT and then immediately doing the IFFT, It worked just fine.

I then decided to again go step by step thru the tutorial -- This time it all worked great; just as your tutorial indicated.

I have no idea what I was doing wrong before.

Thank you so much

SteveD
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  #17  
Old 06-27-2005, 01:28 PM
SteveD SteveD is offline
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FFT filter problem - Solved

Cameraken

Thank you for your post.

I believe you are correct, I think I just turned on the eye.

Thank you all so much.

SteveD
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  #18  
Old 06-29-2005, 04:46 PM
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nebgranny nebgranny is offline
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Well there is a lot of interest in this tutorial , I am trying it as well. I am stuck on step 5, the spots will not change, wonder what I am doing wrong. I am new to using photoshop but you just click on brush and make sure black is selected and then brush over the marks with it right? NEB
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  #19  
Old 06-29-2005, 05:01 PM
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byRo byRo is offline
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Neb, let's try a few things....

- Are you seeing something like the image in step 4 - a grey noisy background with a few white stars?
- Did you leave on ONLY the Red channel in the Channel Palette?
- Is the opacity of the brush high (not 0, at least)?
- Do you have a selection active?
- Is the blending of the brush set to normal?
- If this doesn't help, then you could open another (Non-FFT) image and see if you can paint on that. Then, at least, you'll know if the problem is in the brush or the image.

Any luck now?

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  #20  
Old 06-29-2005, 05:34 PM
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nebgranny nebgranny is offline
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Looking good now, had to set opacity up and mode to normal, everything else ok. Going on to next step now. Thanks Ro Neb
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