146. Adjust Hue, Saturation, and Lightness Manually See Also  144 Correct Color Manually
145 Correct Color, Contrast, and Saturation in One Step 147 Adjust Saturation for a Specific Area 178 Colorize a Photograph
A pixel's color value is defined by three components: hue, saturation, and lightness (or luminance, or luminosity). A pixel's hue represents its location on the color wheel, which is the entire spectrum of colors in the computer's gamut or colorspace. Saturation defines the relative power of that hue within a pixelquantifying, for instance, the range between a clear red (full saturation) to a colorless gray (no saturation). Lightness defines the amount of white in a pixel, from black (no light) to white (all light) to somewhere in-between (light pink). To make individual adjustments to these components of pixels within a given region, use the Adjust Hue/Saturation command. For example, many images taken with digital cameras seem to lack saturation. A boost of saturation by even a few degrees can revive an otherwise dull image, infusing it with excitement and drama.  By reducing the saturation in a color image, you can create a black-and-white photooften with better results than simply converting the image to grayscale. By adjusting the hue of a selected object, you can change its color from red to green, for example. By reducing the lightness of an image's background, you can make it fade into the distanceplacing more importance on the subject of your image. 1. | Choose Enhance, Adjust Color, Adjust Hue/Saturation
KEY TERM  | Saturation The amount of a particular hue present in a pixel. A fully saturated red pixel is bright red; a less saturated red pixel has more gray and its reddish tone is more subtle.
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Open the image you want to correct in the Editor in Standard Edit mode and save it in Photoshop (*.psd) format. In the Layers palette, choose the layer you want to adjust. To restrict your adjustment to a given region of the chosen layer, use a selection tool to select that region. See 70 About Making Selections for an explanation of how selections can be used to restrict changes and adjustments to a designated region.
From the menu bar, select Enhance, Adjust Color, Adjust Hue/Saturation to display the Hue/Saturation dialog box. Enable the Preview check box to see examples of your choices in the image before making them final.
| 2. | Choose Colorize Option Setting
NOTE  | To see an example of colorizing layers to bring life to an old monochrome photo in the aquatint style, see 178 Colorize a Photograph. |
This dialog box has two purposes: The second of these purposes is to give you a way to apply a single hue to the designated region. Colorizing a region in this way eliminates all the area's original color information, replacing it with the values designated by the Hue and Saturation settings. To colorize the designated region and replace color values rather than simply adjust them, enable the Colorize check box. When you do this, the meanings of the sliders change. The Hue slider represents an angle on the color wheel between 0° and 360°, theoretically encompassing all the colors of the rainbow. Saturation is a percentage representing how much of the chosen Hue to apply to the region, while Lightness remains a relative setting between 100 and +100, governing how much white is added or removed. (Technically, sliding Lightness in either direction should remove saturation, but in this case, the Saturation slider remains stable.)
If you're colorizing the designated region, make your adjustment choices from these sliders and click OK to exit the dialog box and skip to step 4. Otherwise, continue to step 3.
| 3. | Or Make Relative Color Adjustments
TIP  | Whereas the Adjust Hue/Saturation command applies changes to all or part of a layer, you can create an adjustment layer that applies a saturation adjustment to several underlying layers in an image. See 94 Create an Adjustment Layer for details. |
With the Colorize option disabled, the purpose of the Hue/Saturation dialog box is to make relative adjustments to one, two, or all three of the color channels in the designated region.
From the Edit drop-down list, select the color channels you want to adjust. The Master option refers to all three (red, green, and blue) in combination. The primary channels (Reds, Greens, and Blues) are represented on this list, as well as the secondary colors (Yellows, Cyans, and Magentas). Yellows refers to the red and green channel, Cyans to the green and blue channel, and Magentas to the blue and red channel.
At this point, the Hue slider represents an angle of adjustment between 180° and +180°. When you adjust this setting, the Hue component values of all pixels in the selected region are adjusted by that amount on the color wheel. For example, a yellow pixel when increased 180 degrees becomes blue.
The Saturation slider represents a percentage of adjustment between 100 and +100. Any non-zero setting represents a degree of increase or decrease of color in the chosen channels. Drag the Saturation slider to the right to increase the saturation of the designated region or to the left to decrease the saturation.
The Lightness slider represents a percentage of adjustment between 100 and +100. Any non-zero setting represents a degree of increase or decrease of whiteness in the chosen channels. Drag the Lightness slider to the right to increase the lightness of the selected color range or to the left to decrease the lightness. If you've chosen Blues, for instance, setting Lightness above zero adds white to the blues in the selected region.
Click the OK button to close the dialog box and apply the adjustments to your image.
| 4. | View the Result
When you're satisfied with the results, make any other changes you want and save the PSP file. Resave the result in JPEG or TIFF format, leaving your PSD image with its layers (if any) intact so that you can return at a later time and make different adjustments if you want.
This example featured a scanned photograph that was damaged from exposure to sunlight for several years, probably clinging to the front door of the refrigerator. My first objective was to restore some of the warm skin tones to Aunt Betty's face. I did this by choosing the Reds channel, moving the Hue setting to +4 to restore some of the yellows that had faded (yellows always fade first from exposure to sunlight), and set Saturation to 20 to help balance her skin tones.
Next, I restored the radiant sunlight on the edges of Betty's sweater and hair by choosing the Yellows channel, setting Hue to +9, Saturation to a relatively high +41, and Lightness to a quite high +63. Now the subject matter looks bright and in the center of the picture once again. I used the Magentas channel as an opportunity to bring back contrast to Betty's face because the print was using magenta tones in the shadows. With the Magentas channel chosen, I set Hue to +11 (taking it more toward the red), Saturation to +9, and Lightness way down to 25. Now Betty's face truly is in the center of the picture.
These adjustments were far from enough to fix the overall picture. I tried to add saturation to the Greens channel, for instance, but the problem with this faded print is that too much of the grass and shrubbery color is made up of elements from the Blues channel. I'll need to make spot adjustments to the garden, perhaps with the Color Replacement tool. And nothing I do with the Hue/Saturation dialog box will help me restore contrast to Betty's two jet-black Scottie dogs. But I have Betty's warm, radiant face smiling at me again, and that's a very good start. Look for this image in the Color Gallery.
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