Using target values to set highlights and shadows (Photoshop)Professional color technicians typically set the highlights and shadows in an image by assigning their lightest and darkest CMYK ink values to the lightest and darkest areas of detail in the image. When identifying the lightest and darkest areas of an image, it's important to identify representative highlights and shadows. Otherwise the tonal range may be expanded unnecessarily to include extreme pixel values that don't give the image detail. A highlight area must be a printable highlight, not specular white. Specular white has no detail, and so no ink is printed on the paper. For example, a spot of glare is specular white, not a printable highlight. Note: You can do the following procedure in ImageReady in the Levels dialog box. To use target values to set highlights and shadows:
When you open Levels or Curves, the eyedropper tool
In most situations when you are printing on white paper, you can achieve a good highlight in an average-key image using CMYK values of 5, 3, 3, and 0, respectively. An approximate RGB equivalent is 244, 244, 244, and an approximate grayscale equivalent is a 4% dot. You can approximate these target values quickly by entering 96 in the Brightness (B) text box under the HSB section of the Color Picker.
![]() Original ![]() Highlight set using average-key target brightness values (B: 96); and highlight set using lower target brightness values (B: 80) The pixel values throughout the image are adjusted proportionately to the new highlight values. Any pixels lighter than the area you clicked become specular white. The Info palette shows the values both before and after the color adjustment. In most situations when you're printing on white paper, you can achieve a good shadow in an average-key image using CMYK values of 65, 53, 51, and 95. An approximate RGB equivalent is 10, 10, 10, and an approximate grayscale equivalent is a 96% dot.You can approximate these same values quickly by entering 4 in the Brightness (B) text box under the HSB section of the Color Picker.
![]() Original ![]() Shadow set using average-key target brightness values (B: 4); and shadow set using higher target brightness values (B: 20) To use Threshold mode to identify the lightest and darkest areas in an image:
Note: The Threshold mode in Levels is not available for CMYK images. The image changes to Threshold mode, and a high-contrast preview image appears. The visible areas of the image indicate the lightest parts of the image if you are dragging the white slider, and the darkest parts if you are dragging the black slider. If a color channel is selected in the Levels dialog box, the black area indicates where none of the given color component exists. ![]() Image preview in Threshold mode |