Adobe 13101332 User Guide - Page 150

Adobe Photoshop Help Using Help | Contents | Index Making Color and Tonal Adjustments Back 150 4 For Method, select an option: • Relative to change the existing amount of cyan, magenta, yellow, or black by its percentage of the total. For example, if you start with a pixel that is 50% magenta and add 10%, 5% is added to the magenta (10% of 50% = 5%) for a total of 55% magenta. (This option cannot adjust pure specular white, which contains no color components.) • Absolute to adjust the color in absolute values. For example, if you start with a pixel that is 50% magenta and add 10%, the magenta ink is set to a total of 60%. Note: The adjustment is based on how close a color is to one of the options in the Colors menu. For example, 50% magenta is midway between white and pure magenta and will receive a proportionate mix of corrections defined for the two colors. 5 Drag the sliders to increase or decrease the components in the selected color. Making quick overall adjustments to an image The Brightness/Contrast, Auto Levels, Auto Contrast, Variations, and Auto Color (Photoshop) commands change colors or tonal values in an image but are not as precise or flexible as the high-end color adjustment tools. They provide a quick and simple way to make overall adjustments. Using the Brightness/Contrast command The Brightness/Contrast command lets you make simple adjustments to the tonal range of an image. Unlike Curves and Levels, this command makes the same adjustment to every pixel in the image. The Brightness/Contrast command does not work with individual channels and is not recommended for high-end output, because it can result in a loss of detail in the image. To use the Brightness/Contrast command: 1 Open the Brightness/Contrast dialog box. (See "Making color adjustments" on page 132.) 2 Drag the sliders to adjust the brightness and contrast. Dragging to the left decreases the level and to the right increases it. The number at the right of each slider value displays the brightness or contrast value. Values can range from -100 to +100. Using the Auto Levels command The Auto Levels command moves the Levels sliders automatically to set highlights and shadows. It defines the lightest and darkest pixels in each color channel as white and black and then redistributes intermediate pixel values proportionately. Because Auto Levels adjusts each color channel individually, it may remove or introduce color casts. By default, this feature clips the white and black pixels by 0.5%-that is, it ignores the first 0.5% of either extreme when identifying the lightest and darkest pixels in the image. This ensures that white and black values are based on representative rather than extreme pixel values. Auto Levels gives good results when an image with an average distribution of pixel values needs a simple contrast adjustment or when an image has an overall color cast. However, adjusting the Levels or Curves (Photoshop) controls manually is more precise. Using Help | Contents | Index Back 150