Tutorial: Frequency Separation for portrait retouching
Posted: Mon Nov 26, 2012 9:07 am
I recently came across some articles extolling the virtues of the "Frequency Separation" technique for retouching skin in portraits. The advantage of that method is that by having the colours and the details on separate layers, the modifications can be done quite easily and quickly while preserving the texture of the skin -- the final result doesn't look like a rubber mask was painted on the face.
All the articles used Photoshop, and I couldn't find any info for doing the same thing in PSP. So, I experimented and here's what I came up with. (N.B., this is for an 8 bits/channel image)
Here's the original image:

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1. Duplicate the Background layer, and name the new layer "Colour".
2. On that "Colour" layer, use Adjust...Add/Remove Noise...Median Filter. Use a large enough aperture so the blemishes and uneven skin colours just begin to disappear:

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3. Copy the blurred "Colour" layer, and paste it in as a new image -- it will be "Image 1", e.g.
4. Use Image...Negative Image to reverse the colours of "Image 1":

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5. Back in the original image, turn off the visibility of the "Colour" layer so that only the original, sharp Background layer is showing.
6. Use Image...Arithmetic with these settings:
Image #1: your original (sharp) image
Image #2: Image 1 (the blurred, negative image)
Function: Add
Channel: All channels
Modifiers:
Divisor: 1
Bias: -128
Clip color values: selected
7. A new image ("Image 2") will be created, looking like a grayscale high-pass image:

Uploaded with ImageShack.us
8. Copy "Image 2", and paste it into your original image as a new layer at the top of the layers stack, naming it "Texture".
9. Set the blending mode of that new "Texture" layer to "Overlay".
Your layers will look like this:

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Now you can use various techniques on the "Colour" layer to smooth out the colours of the blemishes and further even out the tones of the skin. I mostly used the Makeover Tool's "Blemish Fixer", but also selected some areas with the Freehand Selection Tool set to a feather of 8 pixels and applied a Gaussian blur of 8 pixel radius. Dodging and burning also came in handy.
The "Texture" layer is used to remove the last traces of some of the blemishes. I used the "Blemish Fixer" for that.
My quickly done final result:

Uploaded with ImageShack.us
Of course, you can go nuts with the technique (as explained in several of the articles found on the Web)
.
Enjoy!
All the articles used Photoshop, and I couldn't find any info for doing the same thing in PSP. So, I experimented and here's what I came up with. (N.B., this is for an 8 bits/channel image)
Here's the original image:

Uploaded with ImageShack.us
1. Duplicate the Background layer, and name the new layer "Colour".
2. On that "Colour" layer, use Adjust...Add/Remove Noise...Median Filter. Use a large enough aperture so the blemishes and uneven skin colours just begin to disappear:

Uploaded with ImageShack.us
3. Copy the blurred "Colour" layer, and paste it in as a new image -- it will be "Image 1", e.g.
4. Use Image...Negative Image to reverse the colours of "Image 1":

Uploaded with ImageShack.us
5. Back in the original image, turn off the visibility of the "Colour" layer so that only the original, sharp Background layer is showing.
6. Use Image...Arithmetic with these settings:
Image #1: your original (sharp) image
Image #2: Image 1 (the blurred, negative image)
Function: Add
Channel: All channels
Modifiers:
Divisor: 1
Bias: -128
Clip color values: selected
7. A new image ("Image 2") will be created, looking like a grayscale high-pass image:

Uploaded with ImageShack.us
8. Copy "Image 2", and paste it into your original image as a new layer at the top of the layers stack, naming it "Texture".
9. Set the blending mode of that new "Texture" layer to "Overlay".
Your layers will look like this:

Uploaded with ImageShack.us
Now you can use various techniques on the "Colour" layer to smooth out the colours of the blemishes and further even out the tones of the skin. I mostly used the Makeover Tool's "Blemish Fixer", but also selected some areas with the Freehand Selection Tool set to a feather of 8 pixels and applied a Gaussian blur of 8 pixel radius. Dodging and burning also came in handy.
The "Texture" layer is used to remove the last traces of some of the blemishes. I used the "Blemish Fixer" for that.
My quickly done final result:

Uploaded with ImageShack.us
Of course, you can go nuts with the technique (as explained in several of the articles found on the Web)

Enjoy!