Fourier Transformation Technique to Remove Moire and Image Imperfections

[Chris Nicola]

I read with great interest Mike's comments on the Fourier Transformatin tool to remove moire and other image imperfections. I tried to follow the directions using PS Elements but got stuck and need som help please. Does anyone know if there is a tutorial for PS Elements with screenshots?  I have PSE8 and Elements plus. I don't know if elements plus can be adapted to work using Fritz method in the fourth post? I tried but could not find a way? Also can CM with channels be used for this technique? Your advice wolud be appciated.

Kind Regards

Chris Nicola

http://www.curvemeister.com/forum/index.php?topic=62.0

http://home.planet.nl/~ber03728/4n6site/improc/fftplugin/howto.htm

[ggroess]

Chris,
Did you try Mikes original process?  It might seem counter intuitive but it does provide some results.

Greg

[Chris Nicola]

Thanks Greg. I tried it but got stuck bcause I did not fully understand it. I duped the RGB layer and applied a levels  adjustment layer and set the green and blue output levels to zero and that gave me a red fingerprint. Then I applied FFT to the Background layer underneath but could not understand how to proceed from there.

Kind Regards

Chris

[ggroess]

If you started by duplicating the image....

Next you paint in the red layer with a cyan brush set to multiply giving you a black output. C+R=BL
Then you run the reverse FFT on the image and copy the result back to your original as a layer set to Luminence.
Then run Gausian blur as described.

The key is to paint on the RED layer with a Cyan brush.  You are creating a "Pseudo Red" layer by turning off the other colors in the levels adjustment layer. 

Greg

[Chris Nicola]

Thanks Greg. Please let me know if the screenshots are correct.

Screenhot 1. Painting out the stars on the FFT image with a Cyan brush set to multiply.

Screenhot 2. Geting a faded looking result after using inverse FFT

Screenshot 3.  After using inverse FFT Putting the resulting very faded image on top of the original background layer and setting blend mode to luminosity. There is some improvement but there are still imperfections there.

Which layer in the screensot am I supposed to apply Gausian blur to? Layer 0 Copy or Background original?

Kind Regards

Chris

[ggroess]

I believe you blur the copy layer and not the original.

Uou also need to paint out a bit more on the FFT cyam layer.  there are some Rays extending out from a fer points that might be adding back into the image.

Greg

[Chris Nicola]

Thanks for your help with this issue Greg. After studying Mike's method and the links he provided more closely I finally understand how the technique works with PS Elements. It works very well in my opinion, maybe just as well as with the full PS. This is the procedure for those who would like to try with PSE:

1 Download the two plug-ins FFT a iFFT from:
http://home.planet.nl/~ber03728/4N6site/improc/fftplugin/getit.htm
Unzip the zip file and then place the two files in your plug in folder.

2 Open the test image which can be downloaded from:
http://home.planet.nl/~ber03728/4N6site/improc/fftplugin/howto.htm
It is a PNG file so convert the mode to RGB for FFT to work. (Image/Mode/RGB)

3 For the sake of the demonstration I Introduced a green tint to the test file. Right click the original background and select duplicate layer. Please see Screenshot 1

4 Go to filters and under "Fourier Transform", apply the FFT filter to the original Backgroud layer on the bottom. Note FFT does not work on a true layer so thats why it has to be applied to the original Background which has no transparency information. It will not work on the copy above it which is a true layer. Please see Screenshot 2.

5  Apply a levels adjustment to the Background layer and as Mike says select the blue channel from te drop down menu and drag the output slider on the bottom right all the way to the far left so the blue output level is set to zero. Do the same with the Green output slider. The result of the FFT image will look red. Please see Screenshot 3.

6 Click the foreground colour box and select Cyan by typing R 0, B 255, G 255. Select the brush tool and set the brush mode to multiply from the top menu and carefully paint out the stars and diagonal lines but leave the central point of light intact. Please see Screenshot 3 and also the link below for more details on the parts to paint out.

http://home.planet.nl/~ber03728/4N6site/improc/fftplugin/howto.htm

7 Click on the origial background layer and apply inverse Fourier Transform iFFT. The resulting Image will look red. Later you can delete the layers adjustment. Please see  Screenshot 4 and also screensot 5 with the layers adjustment deleted.

8 The problem at this point is the image has lost its colour due to the FFT. If it was originally a black and white image we could leave it as it is. However to bring back the colour in a coloured image another step is needed. Right click the original background layer to which FFT and iFFT has been applied and right click and convert to a layer. Then move the black and white image over the copy of the original image (Green) which still has its colour. Set the blend mode to luminosiy and switch on all the eyes. The colour has now returned. As a finishing touch apply a Gaussian blur of about 2 to the lower coloured image.  (Filter/Blur/Gaussian Blur) This will not blur the resulting image because the details come from the image on top and the lower image just provides the colour when the blend mode is set to luminosity. Please see  Screenshot 6.

I wish to thank Mike and Greg for helping me to understand this very useful technique and of course Alex Chirokov and the site www.4N6site.com for providing the FFT plug in.  If I have made any mistakes in the desription please let me know. I wanted to write out all the details with screenshots in case any other Photoshop Elements users wish to try it out.

Kind Regards

Chris Nicola