Digital Light & Color

Ref 1: http://www.thelightsright.com/VibranceVersusSaturation

Vibrance increases the saturation for an image, but unlike the Saturation command, it includes two important protections:
•Skin tones are protected. This prevents skin tones from taking on a red or yellow cast.
•Highly saturated colors are protected against clipping. This avoids unwanted color shifts and loss of important detail.

Ref 2: ColorCorrect transform discussion: http://www.dl-c.com/board/viewtopic.php?f=4&t=592

Introduction: Something to realize here is the difference between making saturation changes in the RGB color space and HSV color space.

In the RGB color space, saturation is NOT independent of Luminance [gray tone] and when making changes with a RGB Brightness curve, saturations will generally decrease with an increase in Luminance and increase with a decrease in Luminance... ...for the most part, these changes to saturation/Luminance are not objectionable and there is little shift in hues.

But for the HSV color space where Saturation is independent of both Hue and Value [gray tone], it is possible to increase the SkinColor hues/saturations greater than preference when attempting to achieve Mid/High saturation preferences resulting in a strong 'burnt red-orange' appearance to Low/Mid saturations... ...hence the possible need for SkinColor protection for both people and non-people image scenes.

In Ref 2 JSachs points out:

You can't really do this properly with Color Correct since it has no way to increase saturation uniformly. You could perhaps use Color Correct (or possibly the Mask Range Tool) to create a skin tone mask, invert it, and use it with the Saturation transformation to increase the saturation everywhere except where there are skin tones.

The following is a possible approach to generically mask an image's SkinColors [Hues and Saturations of the HSV-H,S color plane (sometimes called a color wheel or in PWP, a color hexagon)] for use with the Saturation transform in HSV and either Preserve: Low or Preserve: Low & High modes.

Copy; 'save'; and open into the PWP work space the following SkinColor reference image: ...end Post 1 of 3...

...continuation...

Part 1: Creating the SkinColor HSV-H,S mask.

(1) Click the reference image and open the Mask Tool - Color Range feature.

(2) Left click near the left edge of the reference image and left click Mask Tool 'Contract'.

(3) Left Click - Hold - Shift near the left edge of the reference image; Drag to near the right edge of the reference image; and Release. The Mask Tool should resemble this: (4) Move the white and black sliders of the H, S, and V color bars as indicated: (5) The final adjusted ColorRange should look like this: where the 0 to 7% Hues have a slight feather; the Saturation range is feathered to 0 and 100%; and the full 0 to 100% Values for the Hue and Saturation ranges are selected. This means that wherever a Hue and Saturation occurs within the selected range at any Value will be masked... (6) Close the Mask Tool. The ColorRange setting will be remembered for a given PWP session unless another color range is selected.

...end Post 2 of 3...

...continuation...

Part 2: Adjusting HSV-S saturations.

(1) Open or click on an image that saturation changes are to be made.

(2) Open the Mask Tool - Color Range feature. The settings of Part 1(5) should appear. Click lower-left Apply Add; creating an 'active' mask on the image. Update the mask to include any additional SkinColors or image areas to be masked. [REMEMBER: if changes are made with the Color Range feature, these now become remembered settings for the PWP session.]

(3) Add a 1 to 3 pixel radius Mask Blur.

(4) Click on the image and open the Saturation transform: 'HSV; Preserve: Low' mode. Move the mask Black slider to a preference. Then re-try using 'Preserve: Low & High' and adjusting the White slider from 0% to see if there is a more preferenced result availabe. The White slider protects/adjusts the SkinColor image areas. When adjustments are complete, click OK and OK or Close the Mask Tool.

Why protecting SkinColors may be important:

Original image [1:1 crop] to have HSV-S saturation adjustment: http://www.brucelindbloom.com/index.htm ... mages.html... Saturation adjustment with no SkinColors protection: HSV Saturation transform; Black/White sliders at +30%; Preserve: Low & High... Saturation adjustment with SkinColors protection: Notice the addition of a protected zone [Black slider = +30%; White slider = 0%] of the cone's H,S plane [red-orange hues] and the retention of detail in its side reflection... ...end Post 3 of 3

--Addendum --

For a more uniform saturation adjustment with protected HSV-H,S SkinColors, there is an additional consideration that arises due to the discontinuity of the HSV-H color space model where Red can have two values: 0 or 100% [0 or 255]...

...with the preceding suggested workflow, this results in a harsher gradient Red to Magenta because there is no feathering added in Part 1(5): Is there an interest to make this gradient softer, matching the Orange to Yellow? For photo realistic images, the difference in protected SkinColor hue/saturation gradients will most likely go unoticed.

--Addendum 2 --

This addendum addresses the Red [HSV-H = 0 or 100% (0 or 255)] hue's discontinuity and how to add a Red to Magenta [HSV-H = 83.3% (213)] gradient approximately equal to the Orange [HSV-H = 8.3% (21)] to Yellow [HSV-H = 16.7% (43)] gradient of Part 1(4).

Substitute for the previously suggested Part 2(2) the following...

Part 2(2) Ammended

(2) Open the Mask Tool - Color Range feature. The settings of Part 1(5) should appear.
...(a) Click lower-left Apply Add; creating an 'active' mask on the image.
...(b) Move the H color bar's right white slider all the way to the right.
...(c) Move the H color bar's left white slider to the right to near the right white slider.
...(d) Move the H color bar's left black slider to the left approximately the same as the right black slider adjustment of Part 1(4).
...(e) Move the left white slider to the right so that it overlaps the right slider....(f) lower-left Apply Add; adding the Red to Magenta gradient to the Part 2(2)(a) 'active' mask.
...(g) Update the mask to include any additional SkinColors or image areas to be masked. [REMEMBER: the settings of the ColorRange feature of the Mask Tool have been changed. If another image is to be processed, re-set the ColorRange by returning to Part 1(1) of the suggested workflow after completing adjustments for the current image.]

...End of Part 2(2) Ammended... ...continue with Part 2(3)...

The following might be a useful reference for understanding the PWP Color Hexagon and various notations used to identify hues and saturations as gray tone percentages or the 0 to 255 range: ...Additional Comment... If you prefer the control offered by curves, try using the ColorCurves transform with a HSV-S smooth curve: [0,0], [10,10], [50,65], [90,90], [100,100] in place of the Saturation transform. By moving the [10,10] and/or [90,90] control point(s) along the default diagonal, one can adjust the amount of Low and/or High saturation preservation; and by moving the [50,65] control point up or down vertically, one can either increase or decrease Mid-saturations. [REMEMBER to invert the mask by changing mask Black to a 100% or preference Amount and changing mask White to a 0% Amount.]

Ask if there are questions... ...perhaps some thought should be given to understanding the question as well as the answer... ;-)

Den,
Just to let you know that there is great interest in what you have posted - however I'm a bit pressed at present so am unlikely to find time to do it justice for a while. But I'm looking forward to increasing the depth of my understanding of this whole subject.
Mike.

Den,

I like this color patch approach to skin color protection. While use of the “similar pixels” mask tool might be a bit more convenient for single images with only one or two subjects, that approach can become a bit tedious when dealing with either multiple images or group pictures.

However, I’m not sure about the general applicability of your color patch. The “Bruce’s Paint Shop Pro Tips Skintones Color Chart” shows a much broader range of hues and saturation levels, and makes some attempt to classify colors for African, Asian, and Caucasian skin colors. I simply don’t have a sufficient variety of images to test all combinations, but I created a trio of Caucasian gradient patches – one each for pallor, midtone, and tanned variants. I then stacked them using the crop/border transformation so that I have a single reference patch that can be scanned to generate the appropriate HSV mask range for Caucasian skin tones.

Of course, this approach can include other objects that fall within the color range, but, so far, it has been a quick and easy task to manually swipe those areas out of the mask.

How about this?

Open HSV-S and activate probe.
Probe the skin you want to remain constant and probe something you want to saturate.
Start vectors around the skin probe and delete the skin probe. Leave these vectors fixed.
Start vectors around the saturation target and delete the probe. Raise the high-end vector as desired.

Is a color/tone in the selected protection range? ...A simple way to determine this is to 'Shift - left Click' on the color in the image and note where the black 'tick' contracting marks are in the Mask Tool's Color Range feature. If the 'tick' is inside the white sliders, the color is included. If not, move the appropriate white slider(s) for the H, S, and V color bars so that it is... ...and perhaps re-adjusting the black slider feathering if needed...