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Advice for attacking wide-spread mold?

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  #11  
Old 06-26-2017, 08:07 AM
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John Wheeler John Wheeler is offline
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Re: Advice for attacking wide-spread mold?

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Originally Posted by tropicmom View Post
I have a better resolution scan of the photo itself, this was just a sample to show how wide-spread the mold is. What method(s) can be used to restore the original colors?
Hi tropicmom

Lots of good suggestions already in this thread.

I usually tackle these problems by fixing the luminosity and subsequently the color. This can be done by a variety of techniques yet hard to recommend a technique as it often depends on the characteristics of the image itself.

Without further information I would start with fixing the luminosity by using the channel mixer adjustment layer set to monochrome and use the sliders to null out the mold luminosity issue. Then I paint back in the correct colors on an additional Layer either based on the original image or starting from scratch with the blend mode set to color.

The reason that starting with a much better copy (preferably a TiFF scan at higher bit depth) is the the JPEG you provided while the luminosity component is not compressed to much, the hue and saturation components are heavily compressed as seen by the pixelation. Makes testing your image for the best recommendation problematic. If you post a much better starting image (even if partial image), there are possible even easier techniques that could work.

The image below shows the original image, and below the luminosity, then the hue, and then the saturation components of your image:
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File Type: jpg mold-channel-breakout.jpg (97.8 KB, 16 views)
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  #12  
Old 06-26-2017, 11:57 AM
skoobey skoobey is offline
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Thumbs up Re: Advice for attacking wide-spread mold?

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Originally Posted by John Wheeler View Post
Hi tropicmom
The image below shows the original image, and below the luminosity, then the hue, and then the saturation components of your image:
Out of curiosity, how do you get to saturation and HUE previews? Through selective color and solar curves, or?

EDIT: (I'm suffering from Madonna syndrome with my spelling apparently).

Last edited by skoobey; 06-26-2017 at 12:05 PM.
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  #13  
Old 06-26-2017, 01:56 PM
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Re: Advice for attacking wide-spread mold?

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Originally Posted by skoobey View Post
Out of curiosity, how do you get to saturation and HUE previews? Through selective color and solar curves, or?
I use Layer Blending Math to create these previews.

I have seen many approaches to this or similar (e.g. using the RGB>HSB filter is close)

First note that the "Luminosity, Hue, and Sat" trio, the "Sat" component that I use is the one the Photoshop defines in the Saturation Blend modes. The reason I bring this up is that a different definition of "Sat" is used in the HSB of the Color Picker.

For Luminosity, I just take the image, place a constant tone Layer above (e.g. white) and set the Blend to Color.

For Hue, (which is defined by the relation ship of the two largest numbers of the trio RGB), while keeping the Hue constant, I scale the RGB values for maximum Brightness (largest RGB value at 255), and also maximum saturation (Minimum RGB value set to 0)

For Saturation, (defined by the numerical separation between the largest and smallest value in the RGB trio), I create a gray level R=G=B that represents that same numerical separation.

What is nice about this approach is that I can take these 3 components and recombine them through blending to create the original image (within rounding error).

I found it very useful in a variety of situations. Just one of those is showing how JPEG (and other compression algorithms) hide their compression by avoiding compressing the luminosity channel (the eye has high acuity there) and when compression Hue/Sat it does more in the dark and very light areas first. What JPEG does is much more complex yet this shows the impact in terms easiest understood in color terms which we use everyday in Photoshop.

I am not sure my description helps yet that is the high level description.
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  #14  
Old 07-03-2017, 11:56 PM
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Re: Advice for attacking wide-spread mold?

Hi
John I am interested in your approach – so I had a go at trying it out because I wanted to understand how you got your different layers. I managed to generate the Luminosity and Hue layers. And I think I got them right, that is:-
For the luminosity layer, I made a white layer and set the blend mode to colour and blended it with the original.
For the Hue layer, I took a Hue and Saturation adjustment layer with Hue set to maximum and blended with the original. (Is that correct? It does not look as bright as yours so I am not sure I got this correct).
But I could not get the Saturation layer. I am assuming you are using a 50% grey layer and blending it with the original somehow but I cannot work out what the blending mode is to generate your result. My screenshot shows a saturation blend – is that correct? Thanks.
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File Type: jpg My-trial.jpg (52.8 KB, 8 views)

Last edited by JoReam; 07-03-2017 at 11:58 PM. Reason: needed to clarify a point
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  #15  
Old 07-05-2017, 01:01 AM
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John Wheeler John Wheeler is offline
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Re: Advice for attacking wide-spread mold?

Hi Jo

You have the Luminosity approach correct yet not the Hue and Saturation.

I took a different approach. I went to the definitions given by Photoshop and then used basic Photoshop math to duplicate what was in the Photoshop reference.

Here is a link toa 756 page Adobe document that covers quite a few topics. There is a section on blend math and part of that includes luminosity, hue, and saturation (it gives you the exact detailed equations used).

The blend math starts on page 324 in section 11.3.5. The Luminosity, Hue, and Saturation section begins in the middle of page 334.

Blends let you add, subtract, multiply, and divide and Channel Mixer Adjustment Layers let you isolate/separate specific channel values for R, G, and B when that is needed by the formulas.

So I started by implementing the exact equations using basic operations as mentioned above. This was for academic purposes.

Now, there are simpler implementations as opposed to the basic detailed math approaches I used yet that has been done by others.

So I suggest if you are really want dig in to all of this, start with the reference and go from there: http://wwwimages.adobe.com/content/d...32000_2008.pdf

Hope his helps you bootstrap up the learning curve.
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  #16  
Old 07-05-2017, 06:58 AM
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Smile Re: Advice for attacking wide-spread mold?

Wow Thanks very much John I will certainly have a look at that.
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