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Color shift, honeycomb texture, and mold ..which Problem to Tackle First?

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  #1  
Old 11-27-2004, 02:27 PM
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Color shift, honeycomb texture, and mold ..which Problem to Tackle First?

I hope someone can give me some guidance about what order to work on the attached picture. As I see it, the picture has at least three major problem areas: color shift, honeycomb texture, and mold? damage.

While I can usually fix each of these problems individually, I'm not sure which I should work on first. I started by using a channel mixer AL which got rid of some of the green from the spots, but that's about it. I used Neat Image on one copy and dust/scratches on another then started thinking I should have fixed most of the damage first?

I don't need anyone to actually DO the repairs, but just some help figuring out the order they should be done in, if that makes sense. Thanks!
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  #2  
Old 11-27-2004, 05:22 PM
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For me, I would clearly use the Healing Brush first to remove mold, dust, etc. By trying to remove the texture first you reduce some of the impact of the mold thru blurring but that just makes it more difficult to see and correct further the problem areas. In using the Healing Brush, it analyses seperately the texture, color and luminosity seperately so once the mold and dust is removed you have a clean textured image to work with.
Next I would do some selective texture removal. I tend to seperate out bright whites and dark areas where texture is hard to see. That way you can maintain critical sharpness in important areas.
If there is any resharpening required, I would do that before doing color adjustments only because sharpening by nature causes color shifts.
My thoughts anyway.

Cheers
Dave
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Old 11-27-2004, 07:27 PM
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Frannymae, you asked a really interesting question here.
I'll give you my answer, which is a bit different to Dave's, and I'll be eagerly awaiting other posts here.

You identified three problem areas:
- color shift,
- honeycomb texture,
- mold? damage.

Of these color shift, for me is definitely the last of all. The color information, as opposed to the luminosity, in any image is always the least important and color blotches are pretty easy to fix.

Honeycomb texture, for me, is definitely the first. This is because the best way I've seen to take out this texture depends on the fact that the pattern is repetitive. If we start the restoration process we will probably break up that pattern.

Actually the very first step of all is what you have done here: STOP and analyse the photo and decide a plan of action, don't go rushing in. (Did I say that? Oh, dear I think I'm getting old)

My sequence:
1) Choose the best luminosty mix - here 100% Red;
2) Take out honeycomb using the Alex-Chirokov-FFT process as posted by tzec here;
3) Heal and/or stamp to take out the major defects on the luminosity image;
4) Follow the steps of Flora's excellent tutorial to recover the best from the luminosity image;
5) Mix the luminosty (blending luminosity) back into the original colored image and unblotch the colors as in this tutorial - Skin Tone Correction - Unclipping.


byRo

Last edited by byRo; 11-27-2004 at 07:55 PM. Reason: put in the links
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Old 11-27-2004, 07:57 PM
Vikki Vikki is offline
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I agree with byRo..texture first, for the reason he stated.
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Old 11-28-2004, 07:08 AM
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FrannyMae FrannyMae is offline
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Thanks for the great imput! I am going to tackle the texture first using the FFT/IFFT method...IF I can figure it out!

I tried using it once before and got the same results. I am obviously missing something.

I have read and reread the directions and am still not clear on the procedure. I tried to run the FFT filter on just the red channel, then cloned out the "stars," then ran the IFFT. But the result is just a channel filled with black. I read that you should use the "HSB filter" before making any corrections but of course I don't know what that is!

And even after I ran the FFT I wasn't sure if I was supposed to clone out every tiny "star," the big giant "star" in the middle, or what! LOL! I am really showing my ignorance in this department. I would love to see what this filter can really do, but I'm stumped. Any guidance? Thanks!
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Old 11-28-2004, 11:45 AM
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Quote:
Originally Posted by FrannyMae
Thanks for the great imput! I am going to tackle the texture first using the FFT/IFFT method...IF I can figure it out!

I tried using it once before and got the same results. I am obviously missing something.

I have read and reread the directions and am still not clear on the procedure. I tried to run the FFT filter on just the red channel, then cloned out the "stars," then ran the IFFT. But the result is just a channel filled with black. I read that you should use the "HSB filter" before making any corrections but of course I don't know what that is!

And even after I ran the FFT I wasn't sure if I was supposed to clone out every tiny "star," the big giant "star" in the middle, or what! LOL! I am really showing my ignorance in this department. I would love to see what this filter can really do, but I'm stumped. Any guidance? Thanks!
1) Make a grayscale image. FFT will work with coloured images, but when you transform back (IFFT) the colour will be gone;
2) Duplicate the image merging the layers so you will have just the flattened "Background" layer (FFT doesn't understand layers)
3) Run the FFT filter (Filters>Alex Chirakov>FFT)
4) Run Filter>Other>HSB/HSL selecting RGB to HSB: If this filter isn't present you'll have to install it. You'll find it on your Photoshop CD (\Goodies\Optional Plug-Ins\Photoshop Only\HSL & HSB Filter) - just copy the "Hsbhsl.8bf" file to your PS filter directory.
5) On the Blue channel, clone out the stars with blending set do Darken, on the Green channel clone using Lighten. Do not touch the bright middle part, just the little stars. Do not touch the Red channel
6) Run the HSB filter returning from HSB do RGB.
7) Run the IFFT (Filters>Alex Chirakov>IFFT) to get back to the original.

Like a lot of things, it's only difficult the first time!
Tutorial? It's on my list.


[Added 25-may-2005: IMPORTANT: If you download the new RGB version of Alex Chirakov's filter from here, then you don't need any of this HSB stuff - you just clone out the stars the the RED channel.]

Last edited by byRo; 05-25-2005 at 06:08 PM. Reason: put in some more details
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Old 11-28-2004, 12:01 PM
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Great post, trying to figure out what to do first seems to be one of my major problem areas also. And I also tried the FFT/IFFT method with limited success. I'll have to try it again per byRo's instructions.
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Old 11-28-2004, 01:24 PM
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Hi Roland

I need a bit more help with your reasoning. You say that by restoring first, you might destroy the integrity of the texture making it difficult to eliminate or reduce afterwards. You also say that eliminating the cast and "yellow mold" should be last.
The most important feature is the face and perhaps the blouse. You can fairly easily identify the edges of the yellow mold, therefore, it should be an easy process to sample surrounding good skin and paint over in color mode. "No" texture is destroyed from what I can determine. Dust and artifacts can easily be eliminated with the Healing Brush. From what I can see, the Healing Brush does not alter the texture beneath. From my test, I end up with an excellent restored image with all the texture intact. From that point it is easy to reduce the texture effect from whatever method works for you. I think also that people will generally have better success using Flora's texture reducing method.

If you remove the texture first, you are essentially blurring the image to some degree, are you not. Therefore the yellow mold will have less distinct edges making it more difficult to colorize it out because it will bleed into the good skin. Sorry. Sometimes I'm a bit thick.

Cheers
Dave
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Old 11-28-2004, 01:38 PM
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The man said his favorite question is "Why?". So I doubt he'll find you "thick" at all. These questions help us all understand things a little better, and I'm glad to see them.

Re: breaking up the texture. If I understand him correctly, he is saying that there's a good chance the honeycomb texture will not align properly if restoration is done first, making it more difficult. But maybe I'm wrong. We'll wait for the official answer.

Ed

Last edited by Ed_L; 11-28-2004 at 04:57 PM.
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Old 11-28-2004, 04:28 PM
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Quote:
Originally Posted by Ed_L
The man said his favorite question is "Why?". So I doubt he'll find you "thick" at all. These questions help us all understand things a little better, and I'm glad to see them.
Re: breaking up the texture. If I understand him correctly, he is saying that there's a good chance the honeycomb texture will not align properly if restoration is done first, making it more difficult. But maybe I'm wrong. We'll wait for the official answer.
Ed
Thanks, Ed, saved me a lot of keystrokes.

FFT first
The FFT method works by giving us a way to identify and eliminate patterns that repeat exactly at a fixed frequency. When we "clone out the stars" we are NOT doing any blurring, we are filtering out just a specific frequency. Frequencies higher (= sharpness) than that of the honeycomb pattern are left unaffected.
I regard this as a safe no-loss first stage exactly because of this. Neat Image and / or Gaussian blur will do the job but these methods do have the price of blurring the image and / or looking un-natural.
When we apply Neat Image / GBlur after FFT, we have to trade-off much less sharpness to take out the noise.

Healing brush
We seem to have a difference of opinion as to the healing brush. To me it does change the texture when applied. Maybe on this photo it looks the same to our eyes, but it does break up the pattern integrity.

Color last
As the FFT method only works on grayscale images it is natural to do the luminosity and color corrections separately.
Maybe it's just a personal preference thing, but I always seem to end up fixing the luminosity image first and only when that's as good as it's going to get, do I go for the colors.

Flora's method
I do recommend Flora's texture reducing method, all I am doing is trying to make it easier to apply by taking out the deepest texture first.

Ed / Dave - sometimes I write like I know all the answers, it's a problem I have always had. I'm learning new things every day and little discusion like this is good for all of us. Thanks.

Cheers!

Last edited by byRo; 11-28-2004 at 06:27 PM. Reason: fixed the typo
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