Working with the Color Controls

You use the Color adjustment controls to selectively adjust the red, green, blue, cyan, magenta, and yellow colors in an image. Each color has individual Hue, Saturation, and Luminance controls. If you need to adjust the hue, saturation, and luminance of a color that does not appear in the Color controls, you can use the Color eyedropper to identify a hue in the image that needs adjusting.

Although segmenting control of hue, saturation, and luminance on a per-color basis may seem complicated at first, restricting these adjustments to specific colors helps correct and enhance targeted colors without affecting others. In addition, Aperture provides Range controls used to set the extent of colors affected by the Hue, Saturation, and Luminance adjustments. The extent of colors affected by these adjustments is also known as chromatic spread. You use the Range controls to fine-tune your color adjustments.

Figure. Image before and after a Color adjustment.

You can also brush the Color adjustment on selected parts of an image. For more information, see Making Brushed Adjustments.

About Hue, Saturation, and Luminance

Hue (H) describes the actual color itself. Hue is measured as an angle on a color wheel. Moving a Hue slider in Aperture remaps the color from its original position on the color wheel to the new position indicated by the slider. Hue adjustments are often made to match the color of the same subject in different images. Adjusting the hue of an image is particularly useful when the subject you shot moved between various lighting conditions. Another advantage of adjusting the hue of an image is that camera models of different types or from different manufacturers rarely capture and render color exactly the same way. You can use the Hue controls to match the color of a subject shot by two different cameras, so that when the images are placed side by side, they match.

Saturation (S) defines the intensity of a specific hue. A saturated hue gives the color a vivid and pure appearance. A less saturated hue appears flatter and more gray. A completely desaturated hue becomes a shade of gray.

Luminance (L) describes the brightness of the selected color. An increase in luminance brightens the selected color value. A maximum Luminance adjustment results in pure white. Conversely, a decrease in luminance darkens the selected color. A minimum Luminance adjustment results in pure black.

Figure. Illustration of hue, saturation, and luminance on a color wheel.

Adjusting the Color of the Image with the Color Controls

When you want to adjust the color values in an image, you must first identify the colors that have the most influence on the colors you want to change. It’s important to understand that you’re adjusting the colors of the image within the RGB spectrum; therefore, you reduce yellow when you increase blue, you reduce magenta when you increase green, and so on. When you want to isolate a color and adjust its hue, it’s important to identify the color’s location on the color wheel. For example, if the color value is closer to cyan than blue, you may decide to adjust the cyan Hue value without adjusting the blue Hue value. Depending on the image, you may decide to adjust both the cyan and blue Hue values to achieve the color values you’re looking for. There’s not just one correct way of perfecting the colors in an image. Your approach should be based on the image’s subject and the overall aesthetic you want to achieve.

Figure. Illustration showing a remapping of the color cyan by 4 degrees on a 360-degree color band.
To adjust a color value in an image
  1. Select an image.

  2. In the Color area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, click the color button that corresponds to the color you want to adjust to view its Hue, Saturation, Luminance, and Range controls.

    Note: You can also click the Expanded View button to expand the Color area to show the controls for all colors at the same time.

    Figure. Expanded view of the controls in the Color area of the Adjustments inspector.
  3. If a Hue adjustment is necessary, adjust the Hue parameter by doing one of the following:

    • By default, the Hue slider is set to the center of the slider control. Drag the Hue slider to the left or right to change the hue of the selected color.

    • Click the left or right arrow in the Hue value slider to change the hue of the selected color in the image by single increments, or drag in the value field.

      The left arrow remaps the hue in the following ways:

      • Red Hue value moves toward magenta.

      • Yellow Hue value moves toward red.

      • Green Hue value moves toward yellow.

      • Cyan Hue value moves toward green.

      • Blue Hue value moves toward cyan.

      • Magenta Hue value moves toward blue.

      The right arrow remaps the hue in the following ways:

      • Red Hue value moves toward yellow.

      • Yellow Hue value moves toward green.

      • Green Hue value moves toward cyan.

      • Cyan Hue value moves toward blue.

      • Blue Hue value moves toward magenta.

      • Magenta Hue value moves toward red.

    • By default, the Hue value slider is set to 0.0. Double-click the number in the value slider, then enter a value from –180.0 to 180.0 and press Return.

      Figure. Hue controls in the Color area of the Adjustments inspector.
  4. If a Saturation adjustment is necessary, adjust the Saturation parameter by doing one of the following:

    • By default, the Saturation slider is set to the center of the slider control. Drag the slider to the left to desaturate the selected color, or drag the slider to the right to increase the saturation of the selected color.

    • Click the left or right arrow in the Saturation value slider to change the saturation of the selected color in the image by single increments, or drag in the value field.

    • By default, the Saturation value slider is set to 0.0. Double-click the number in the value slider, then enter a value from –100.0 to 100.0 and press Return.

      Figure. Saturation controls in the Color area of the Adjustments inspector.
  5. If a Luminance adjustment is necessary, adjust the Luminance parameter by doing one of the following:

    • By default, the Luminance slider is set to the center of the slider control. Drag the slider to the left to decrease the brightness of the selected color, or drag the slider to the right to increase the brightness.

    • Click the left or right arrow in the Luminance value slider to change the brightness of the selected color in the image by single increments, or drag in the value field.

    • By default, the Luminance value slider is set to 0.0. Double-click the number in the value slider, then enter a value from –100.0 to 100.0 and press Return.

      Figure. Luminance controls in the Color area of the Adjustments inspector.
  6. The Range parameter limits or expands the chromatic range of the adjustment. Adjust the Range parameter by doing one of the following:

    • By default, the Range slider is set to the center of the slider control. Drag the slider to the left to decrease the range of the selected color, or drag the slider to the right to increase the range.

    • Click the left or right arrow in the Range value slider to change the chromatic range of the selected color by 10 percent increments, or drag in the value field.

    • By default, the Range value slider is set to 1.00. Double-click the number in the value slider, then enter a value from 0.00 to 20.00 and press Return.

      Figure. Range controls in the Color area of the Adjustments inspector.
      Figure. Illustration showing chromatic range on a 360-degree color band.
  7. Repeat steps 2 through 6 until you are satisfied with the appearance of the colors in your image.

Adjusting Custom Colors Using the Color Eyedropper

If you require a more specific hue as a starting point for your color adjustment, you can use the Color eyedropper to identify a hue in the image.

To adjust a custom color value in an image
  1. Select an image.

  2. In the Color area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, click the color button with the hue closest to the one you plan to adjust, then select the Color eyedropper tool.

    Figure. Color eyedropper tool in the Color area of the Adjustments inspector.

    The pointer changes to an eyedropper, and the Loupe appears, showing a magnified view of the target area. By default, the Loupe is set to magnify the image to 100 percent (full size). If necessary, you can increase the magnification of the Loupe by pressing Command–Shift–Plus Sign (+). For more information about the Loupe, see Viewing Images with the Loupe.

  3. Position the eyedropper over the color in the image that you want to adjust, then click.

    Figure. Loupe showing a magnified view of an area of green in the image.

The new hue is selected and becomes the starting point for color adjustments of that hue. For more information about Color adjustments, see Adjusting the Color of the Image with the Color Controls.