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FFT Filter for Photoshop CS4

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Old 07-23-2010, 09:51 PM
kmmbkworm kmmbkworm is offline
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FFT Filter for Photoshop CS4

Have used Photoshop since Version 6 and even taught Photoshop for four years but have never heard of a FFT filter for Photoshop. Could someone please explain an FFT filter? I gather it must be purchased as a plugin. Also, I use a Mac running CS4 and need to know where I could purchase the filter for my system. I have owned a small photo restoration business for nine years and constantly run into the problem of removing paper texture from scans. Usually the techniques I learned from Katrin Eismann and Ben Willmore's books work just fine but am having a problem with a current project. Researched all the many Photoshop books I own as well as training DVDs and there is no mention of an FFT filter anywhere - could it possibly have another name? Completed research online and saw something about an FFT filter. Read through a thread on RetouchPro from 2008 about problems with a FFT filter but no clear explanation about what the FFT filter actually does. Can someone please help?
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Old 07-23-2010, 11:07 PM
Stecyk Stecyk is offline
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Re: FFT Filter for Photoshop CS4

FFT stands for Fast Fourier Transform. I recall this vaguely from my studies at university many moons ago.

Rather than me trying to explain it, here's two links that do a better job:

http://www.skeller.ch/ps/fft_action.php

http://www.tipsquirrel.com/index.php...educe-texture/

Those who appreciate the supporting math:

http://www.student.kuleuven.be/~m021...G/fourier.html

Using your favorite search engine, you can probably find several more links. To come back to your original post, I suspect that the FFT will help you tremendously. The second link has an example of textured paper.
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Old 07-23-2010, 11:09 PM
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mistermonday mistermonday is offline
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Re: FFT Filter for Photoshop CS4

kmmbkworm, welcome to RetouchPro. FFT stands for Fast Fourier Transform and is a mathematical algorithm used to calculate a Discrete Fourier Transform and its inverse. Its pretty intense mathematics which finds applications in a wide range of engineering fields. With respect to digital images it can be used to filter repetitive patterns such as the honeycomb or similar patterns used in photographic paper notably in the 1970's and 80's. There are a number of FFT filters for digital images. I am not sure what is available for the Mac but a notable one for PCs is called Image Analyzer by Meesoft. A free version is available at Meesoft.com.
Regards, Murray
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Old 07-23-2010, 11:25 PM
kmmbkworm kmmbkworm is offline
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Re: FFT Filter for Photoshop CS4

Thanks to both Stecyk and mistermonday. I will follow all the leads you both provided. I don't understand how I could work with PS for so many years and so many versions and never hear a word about a FFT filter or fast fourier transform. I work extensively with channels, curves, layer masks, adjustment layers, etc., and have never heard of an FFT filter. I have also attend NAPP conferences for years and have never heard anyone mention it at one of the seminars I attended. It does sound like a filter I can certainly benefit from using. Has it always been a plugin or was it once included in PS? I have studied books and training DVDs by Katrin Eismann, Ben Willmore, Jack Davis, Barry Haynes, Dan Margulis, and of course, Scott Kelby, but can find no mention of an FFT filter. Why is it such a well-kept secret?
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Old 07-24-2010, 04:12 AM
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0lBaldy 0lBaldy is online now
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Re: FFT Filter for Photoshop CS4

Quote:
Originally Posted by kmmbkworm View Post
Completed research online and saw something about an FFT filter. Read through a thread on RetouchPro from 2008 about problems with a FFT filter but no clear explanation about what the FFT filter actually does. Can someone please help?
Welcome to RetouchPRO Hope you enjoy your stay here and make lots of friends. Poke around, ask questions, offer help, have fun!

FFT and IFFT are built into ImageJ (open source, free, Mac Compatible)

Maybe these links will provide some insight to the FFT filter:

http://www.roborealm.com/help/FFT.php

http://www.qsimaging.com/ccd_noise_interpret_ffts.html

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

http://image.bio.methods.free.fr/lsmtransfftset.html

To repair most paper textures captured during a scan... using imageJ:

OPEN IMAGE.... Process>FFT>FFT, click magnifying glass and increase magnification to at least 50%% or more.....Image>Adjust>Brightness/Contrast (till you can see all the little white spots and your cursor), double click on pencil or brush ... adjust size a little bigger than the spot ~~~ paint each spot black except for the large center bright spot and the dividing lines ..... when finished covering all the spots.... Process>FFT>Inverse FFT.... save image with new name

It may seem like a secret because of all the other scientific uses of the Fourier transform... such as engineering, physics, applied mathematics, and chemistry... besides being sort of complicated to fully understand ( I know I do not have a clue.. except for a very few instances to use it within Photoshop)
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Old 07-24-2010, 09:50 AM
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skydog skydog is offline
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Re: FFT Filter for Photoshop CS4

Think of the texture you are having issues with...it has a pattern which is repeditive...it is not random...this pattern (frequency) is more prevalent than any other frequency (noise) in the photo. Fourier looks and all the noise and provide a distribution (ranking) of the frequencies. In the case with the pattern in the picture, this frequency would occur more often and be the highest rank. The spot that Baldy mentions above are those most occuring frequencies. When you paint them out you are basically erasing this frequency (pattern) from the photo.
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Old 07-24-2010, 02:26 PM
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TommyO TommyO is offline
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Re: FFT Filter for Photoshop CS4

kmmbkworm,
Don't feel bad, as FFT has generally only been discussed in the restoration or scientific communities, not the general Photoshop community. In addition to all the other good links and information provided by others above, here is one more that does a good job of explaining the math and some applications.


FFT Math Explained at the University of Edinburgh


The older FFT filters has some limitations with regard to the maximum number of pixels they could handle (30,000 pixels I think). So, as images got larger, the filters fell out of favor.

ImageJ is java based, so should work fine on any operating system. ImageJ also contains many many complex image manipulation algorithms.

The hard part of using FFT filters is remembering the actual steps. Since we don't use it often, it just doesn't come naturally. For example, the older FFT filter for PS had be used on a copy of the merged layers, then you had to paint out the offending frequencies on the one color channel used to stored the FFT results, then run the inverse and blend that back in to the original, etc., etc. So, others developed some actions to make the steps easier. However, the magic was always in the ability to paint out the offending frequencies. So, others also developed some really nice brushes to make the painting process easier. ( I happen to like those created by byRo, here on RP.) The brush /editing tool provided by ImageJ is a bit harsh, but seems to do the job. In fact, byRo was involved in most of the FFT discussions in the early 2000's here on RP. So, to learn more, just do an advanced search here on RP for FFT posts by byRO, or OlBaldy .
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Old 07-24-2010, 02:43 PM
Stecyk Stecyk is offline
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Re: FFT Filter for Photoshop CS4

Using TommyO's helpful information, I have three more links to share:

One: http://www.retouchpro.com/forums/rp-...r-texture.html

Two: http://retouchpro.com/tutorials/?m=show&id=185

Three: http://forums.dpreview.com/forums/re...ssage=16172756

The third link seems helpful in that there is an url link to an action.
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Old 07-25-2010, 10:03 PM
kmmbkworm kmmbkworm is offline
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Re: FFT Filter for Photoshop CS4

My thanks to everyone - TommyO, skydog, Stecyk, OlBaldy, and mistermonday - who responded so quickly and thoroughly to my inquiry. I did download Imagej on my Mac but did not get the results I had hoped for with the image. Next I downloaded the Alex Chirakov filter to load on my husband's PC on which I run PS CS2 as a backup. The tutorial from RetouchPro for the filter is wonderful. Had no problem following it. While the results were better than I had achieved previously, it still is not what I was hoping for. To be honest I think what I was hoping for was a miracle. While I can see a lot of use of the FTT filter in the future, this photo was just not meant to be. It started as a 1976 snapshot taken inside a church with poor lighting, 3.5 x 3.5. I cropped the bride and groom out of the center of the image as they walked down the aisle. Then enlarged the crop to 5x7. To put it mildly, the texture of the image is pronounced. Oh well, I got 19 snapshots looking great, much better than the original images. The client is using the images in a photo book to create a gift for his wife for their 35th wedding anniversary. The couple did not hire a photographer for their wedding. Just gave the guests camera to take point and shoot images so you can imagine what the images came out like. This time I ran the FFT filter on the entire snap shot before I cropped and enlarged the bride and groom. Much better results. Thank again to everyone, so thankful I have found RetouchPro.
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Old 07-25-2010, 10:54 PM
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gholmes1936 gholmes1936 is offline
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Newbie Re: FFT Filter for Photoshop CS4

Quote:
Originally Posted by kmmbkworm View Post
My thanks to everyone - TommyO, skydog, Stecyk, OlBaldy, and mistermonday - who responded so quickly and thoroughly to my inquiry. I did download Imagej on my Mac but did not get the results I had hoped for with the image. Next I downloaded the Alex Chirakov filter to load on my husband's PC on which I run PS CS2 as a backup. The tutorial from RetouchPro for the filter is wonderful. Had no problem following it. While the results were better than I had achieved previously, it still is not what I was hoping for. To be honest I think what I was hoping for was a miracle. While I can see a lot of use of the FTT filter in the future, this photo was just not meant to be. It started as a 1976 snapshot taken inside a church with poor lighting, 3.5 x 3.5. I cropped the bride and groom out of the center of the image as they walked down the aisle. Then enlarged the crop to 5x7. To put it mildly, the texture of the image is pronounced. Oh well, I got 19 snapshots looking great, much better than the original images. The client is using the images in a photo book to create a gift for his wife for their 35th wedding anniversary. The couple did not hire a photographer for their wedding. Just gave the guests camera to take point and shoot images so you can imagine what the images came out like. This time I ran the FFT filter on the entire snap shot before I cropped and enlarged the bride and groom. Much better results. Thank again to everyone, so thankful I have found RetouchPro.

Could you give us an example of a "before" photo? Somebody here maybe able to help with other suggestions.
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