Clipping Display

The Levels dialog box has one very useful, rather hidden feature for identifying the darkest and lightest areas in an image, thus making it easier to set the black and white end points. When you hold down Alt (Windows), Opt (Mac OS) and move the Input Levels sliders, a high-contrast image is displayed, which makes it easier to identify the darkest and lightest part of the image (Figure 3-35).

Figure 3-35: Top—Image being viewed in normal mode. Bottom—Same image viewed in Threshold mode in order to identify shadow data.

Here's how it works: When you move the black Input Levels slider to the right, the darkest parts of the image are made visible first and, as you move the slider up the scale, the lighter parts of the image become progressively visible until only the very lightest remain visible. The reverse happens when you move the white Input Levels slider to the left.

You can also use Threshold mode to find the threshold levels in individual channels. To do so, simply select the channel from the Channels pop-up menu in the Levels dialog box and then proceed as previously described.

NOTE The Threshold mode is not available to images in CMYK, Lab, Indexed Color, or Bitmap mode.

0 0

Post a comment