Working with the White Balance Controls

You use the White Balance adjustment controls to change the color temperature and color tint of an image. If an image has pixels that are supposed to be pure white, you can use the White Balance eyedropper to automatically adjust the color temperature and tint, or you can adjust the color temperature and tint manually. In most cases, the automatic adjustment succeeds in removing the color cast from the image. If the White Balance eyedropper does not completely remove the color cast from the image, you can use the Temp and Tint adjustment controls to fine-tune the adjustment.

Although Aperture can set the white balance of the image with great accuracy, sometimes you have to use a combination of these two methods to have the image appear with the warm or cool tonality you intended.

Figure. Image before and after a White Balance adjustment.

Adjusting White Balance with the White Balance Eyedropper

When you have pixels in your image that should be pure white, you can use the White Balance eyedropper tool to automatically set the color temperature and tint of the image. All you have to do is use the White Balance eyedropper to select a portion of the image that contains neutral gray pixels, and Aperture white balances the image instantaneously.

To adjust the color temperature and tint with the White Balance eyedropper
  1. Select an image.

  2. In the White Balance area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, select the White Balance eyedropper.

    Figure. White Balance eyedropper tool in the White Balance area of the Adjustments inspector.

    The pointer changes to the Loupe, 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 target area of the Loupe over the pixels in the image that are a neutral gray, then click.

    Figure. Loupe magnifying an area of the image with neutral gray pixels.

The white balance of the image is adjusted. The color tonality of the image is shifted either cooler or warmer, depending on the tonality of the original image.

Important: Make sure that there is as little digital noise in the target area of the Loupe as possible. Digital noise can skew the white-balance calculation results, introducing a color cast that wasn’t previously there. A simple way to avoid errant pixels is to increase the magnification of the Loupe by pressing Command–Shift–Plus Sign (+).

Adjusting Color Temperature with the Temp Controls

You can also adjust the color temperature of an image manually using the Temp parameter controls. Color temperature is a term used to describe the color of light when the image was shot. However, it refers to the color value of the light rather than its heat value. Light’s color temperature is measured in units called kelvin (K). Adjusting the color temperature of the image changes how Aperture interprets the colors in the image in relation to the assigned temperature of light. The purpose of adjusting the color temperature of an image is to make colors look as natural as possible.

To manually adjust the color temperature of an image
  1. Select an image.

  2. In the White Balance area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, adjust the Temp parameter by doing one of the following:

    • Drag the Temp slider to the left to cool the tonality of the image, or drag it to the right to warm the tonality.

    • Click the left or right arrow in the Temp value slider to change the brightness of the image by 10 K increments, or drag in the value field.

      The left arrow decreases the color temperature of the image, and the right arrow increases the color temperature.

    • Double-click the number in the Temp value slider, then enter a value from 2000 K to 50,000 K and press Return.

      Figure. Temp controls in the White Balance area of the Adjustments inspector.

The color temperature of the image is updated as you change the parameter value.

Adjusting Tint with the Tint Controls

You can also manually adjust the tint of an image using the Tint parameter controls. You use the Tint parameter controls when you need to fine-tune the white balance adjustment by neutralizing the remaining green or magenta tint.

To manually adjust the tint of your image
  1. Select an image.

  2. In the White Balance area of the Adjustments inspector or the Adjustments pane of the Inspector HUD, adjust the Tint parameter by doing one of the following:

    • Drag the Tint slider to the left to add a green tint to the image, or drag it to the right to add a magenta tint.

    • Click the left or right arrow in the Tint value slider to change the tint of the image by single increments, or drag in the value field.

      The left arrow adds a green tint to the image, and the right arrow adds a magenta tint.

    • Double-click the number in the Tint value slider, then enter a value from –150 to 150 and press Return.

      Figure. Tint controls in the White Balance area of the Adjustments inspector.

The image’s tint is updated as you change the parameter value.