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FFT FILTER WITH PHOTOSHOP ACTION

 

Foreword:
The FFT (Fast Fourier Transform) filter can be used to remove some of the pattern noise (uniform pattern of texture) often seen when old photos with textured paper are scanned. Even though it won't work all the time and it will not remove all the artifacts, I found this to be an invaluable tool and use it often as the very first step BEFORE starting to retouch and restore the image.

To speed things up, I've created a small action for Photoshop, which you can download at the bottom of this article. The method used is based on the tutorial written by Roland Wyant, which has some interesting information in the discussion following his tutorial too. The FFT filter used in this action (RGB version of FFT/IFFT) has to be downloaded and installed first. You can find the filter at the end of this article.

 

FFT original

 

[1] Run the FFT action up to the first dialog, where you will have to stop it. You should have an image looking like the one beneath and even though the pattern might be different, it will most likely have a couple of "stars".

FFT stars

 

[2] As prompted, use a soft black brush and paint the stars, except the big one in the middle. Better yet, use the FFT brush for more accurate and easier painting (download at the end of this article). Having done that, it should look something like this:

FFT stars painted

 

[3] Now resume the action. If you are in the button mode, the gray button should be red, so you can simply click on it again. If you are in the standard mode, press the play button to continue the action. You should end up with your original image and a new layer on top of it by the name of FFT. Here is what my sample looks like at this point:

FFT after action

 

[4] From now on, it will depend entirely on your result, if you want to continue addressing the texture or start with your cloning and other fixes. I found that noise reduction plug-ins like NeatImage as an example, do a very good job of cleaning up the rest but this might not always be needed or doesn't give you the result you are looking for.

For this example and because of my workflow, I have converted the resulting image to LAB and continued my work there. This is mainly because I do my color correction and cloning in LAB, so if your workflow is different, you can skip this and go to the bottom of the article to download the action now, otherwise keep on reading.

 

[5] In LAB, I had a quick look at the A and B channels, just to find that I still have that pattern. To improve this, I've duplicated the background layer and blurred the A and B channel. Which filter to use will depend on your image. In my case, I've used Surface Blur on one channel and Median on the other but you can also use Dust & Scratches, Smart Blur or Gaussian Blur as an example. Try keeping as much detail as possible but eliminating the pattern.

FFT lab blur

 

[6] Working on a duplicate layer allows me to lower the opacity if I went too far with blurring. Having done that, I still had some of the pattern left in the luminosity layer but with this one I had to be very careful, otherwise all detail will be destroyed. Again, rather than working on the FFT layer, I've created a new layer on top and stamped all layers into it. I then ran Surface blur on the lightness channel and reduced the opacity to 30%.

FFT layers palette

 

[7] Working with FFT introduced some contrast changes and to be honest, my original scan wasn't that good either, so I needed to adjust the color and the contrast. In LAB, one curves adjustment layer can take care of this and I ended up with this:

FFT final

 

[8] The rest is the usual cloning, further tweaking, sharpening and whatever you like to do but I suggest that if you do have such pattern noise, take care of it first. As always, if you can get a better scan or setup proper lighting and take a picture of it instead, I would suggest you do that, rather than trying to fix it in Photoshop.

 

FFT action: FFT action (for the new FFT filter from 3D4X, use this FFT action instead)
FFT filter for PC: Download it from this site or from 3D4X (courtesy of Alexandre Chirokov)
FFT brush: FFT brush (courtesy of Wray Bowling).

 

Thanks to Roland Wyant for the tutorial on FFT and help with proof reading/testing
Thanks to Alexandre V. Chirokov for the FFT filter
Thanks to Wray Bowling for the FFT brush
Posted: Updated September 22, 2009 (tested with PS 7.0, CS2, CS3)

 


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