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Using info from green channel, any help?

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  #1  
Old 12-05-2005, 09:51 PM
RobArnold RobArnold is offline
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Using info from green channel, any help?

Hi,
First post here. I've gotten some really good ideas in the past from other posts, hope someone can help me on this one. I know that the damage in this photo is (mostly) in the red channel. I know that I want to take the good info from the green channel to get rid of the red splotches, but that's where I get stuck, because it's not a large section of the photo that's damaged, just the spots. Can someone offer some suggestions?

Thanks
Rob
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Old 12-05-2005, 10:53 PM
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mistermonday mistermonday is offline
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Sue Photo

Here is a quick 3 minute fix without having to do a lot of rubber stamping. It involves moving the image out of RGB and into LAB Color Space. A quick blur of the A and B channels gets rid of most of the junk. Adjust the contrast of the L. Use the healing brush (or rubber stamp) tool to fix the long scratch in the L channel and a few of the remaining small spots. Convert back to LAB.
Regards, MM
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  #3  
Old 12-06-2005, 03:42 AM
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bart_hickman bart_hickman is offline
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Like you said, most of the error is in the red channel, so I created a luminance layer and also split the image into R,G, and B and did heavy NR on the red taking care to manually sample the red splotches so the NR tool would clobber that specifically. Recombined R,G,B and then "luminance" blended the luminance layer into the RGB layer. Now the image pretty much has fuzzy errors in the red channel which is easy to remove with a darken layer (I use a darken layer because the error is mostly too much red--never too little).

So I created this darken layer above the result of the previous step and eyedrop sampled colors near the fuzzy red errors and then paint on the darken layer over the fuzzy red errors--this basically brings the red down to the level of surrounding areas. I had the brush very soft and set to about 40% opacity. This is fairly forgiving of sloppy brush work due to the small change in only one channel and the fact that the opacity is 40%.

Finished off with one last run through the NR tool with standard settings, although I partially protected the hues in her face. Also had some sharpening in the NR tool.

Bart
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Old 12-06-2005, 06:08 AM
RobArnold RobArnold is offline
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Thanks guys. I tried the LAB approach (What does that give me over RGB?) and here's my attempt. Gettin there, I think. Basically blurred A and B channels and then adjusted levels in L channel.

Sorry to be daft about this but it's too early in the morning. What does NR mean?
Rob
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Old 12-06-2005, 08:50 AM
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mistermonday mistermonday is offline
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Sue Photo

Rob, I think by NR he means Noise Reduction. As for LAB Color space, it is a unique space which separates color from contrast. Unlike RGB which defines both color and contrast / luminosity in each channel, LAB separates the contrast / lightness into the L channel and all of the color is in two complex channels called A and B. LAB requires some different thought processes to use but is very powerful for retouching and color correcting. You can heavily blur the A and B channels without having visible negative impact on the compositie image because all of the detail is derived from the L channel. You can do a lot of work to fix up the flaws and adjust the contrast to restore the L and thereby the whole image. Also FYI, a small movement of the curves in A & B allows you to easily shift the hue of the layer. In my tweak of your image, I did a curve adjustment (ctrl M) by selecting the A channel, clicking on the bottom point of the slope and dragged it very slightly to the right. This shifted the cast from Red toward Green. I di it just enough to make her hair more blond. Regards, MM
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Old 12-06-2005, 09:12 AM
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Craig Walters Craig Walters is offline
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yes, NR is noise reduction or noise removal. either works. in psp 10, there's a 'digital camera noise removal' tool if you want a reference for it.

Craig
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Old 12-06-2005, 04:01 PM
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Peter S Peter S is offline
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Worked on this one very quickly - not perfect but I don't think that bad.

Decided to get rid of red and blue channels and the recoloured using the info in the green cannel only.

removed some of the noise

not to happy with the mouth but it was done very quickly

Peter
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Old 12-06-2005, 04:33 PM
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Cameraken Cameraken is offline
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Hi Rob.
Welcome to Retouch Pro.

This is the first picture I’ve ever repaired using LAB. I just followed MM’s method.
And then did a little colouring back in RGB.


Ken
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Old 12-07-2005, 07:04 AM
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Flora Flora is offline
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Hi,

Rob,

Welcome to RP!

I had a go at your picture...

I worked in RGB mode and even though I use the channels regularly for this kind of problem (colour splotches), I didn't here since it wasn't tthat wide spread ... what I did is:

* Created a new blank Layer on top and set its blending to Color.

* Using a very soft brush (Opacity 30-40%), I sampled colour from areas surrounding the red splotches and simply painted on them and repeated it if necessary.

* I used Selective Colors and Color Balance to fix the rest of the colouring.

* To remove most of the noise, I used Neat Image a noise removing software which can be downloaded free here.

* Brightness&Contrast to imrpove the contrast.

* USM to sharpen.
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