Use the Levels feature to correct images with a high concentration of pixels in the highlights or shadows. An image with a full tonal range should have a high number of pixels in all areas: the highlights, the midtones, and the shadows. The Levels filter sets the darkest pixels (the shadows) and the lightest pixels (the highlights) as black and white, and then redistributes the midtones proportionally. This produces an image with the sharpest detail in all of its pixels.
Original with pixels concentrated in the highlights
After adjusting image with Levels
Use the Histogram in the Levels dialog box to view the pixel distribution of an image.
The Histogram is a graphical illustration of the distribution of pixels in the highlights, midtones, and shadows of an image. The Histogram appears in the Levels dialog box.
Histogram
Use the Histogram to determine the best method of correcting an image's tonal range. A high concentration of pixels in the shadows or highlights indicates that you could improve the image by applying the Levels or Curves features.
The x-axis illustrates the color values from the darkest (0) to the brightest (255). Read the x-axis from left to right; the left depicts the darker pixels and the right depicts the brighter pixels. The y-axis depicts the number of pixels at each brightness level.
To adjust highlights and shadows:
| 1 | Select the image in either object mode or image edit mode. |
| 2 | Choose Xtras > Adjust Color > Levels. The Levels dialog box opens.
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| 3 | Choose Preview to view your changes in the workspace. As you make changes, the image updates automatically. |
| 4 | From the Channel pop-up menu, choose whether you want to apply changes to individual colors or to all color channels. |
| 5 | Drag the Input Levels sliders under the Histogram to adjust the highlights and shadows. |
| The slider on the right adjusts the highlights using values from 255 to 0; the slider on the far left adjusts the shadows using values from 0 to 255. As you move the sliders, the values are automatically entered in the Input Levels boxes. | |
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Note: The shadow value cannot be higher than the highlight value, and the highlight value cannot be less than the shadow value.
| 6 | Drag the Output Levels sliders to adjust the contrast values in the image. |
| Drag the right slider to adjust the highlights using values from 255 to 0, and drag the left slider to adjust the shadows from 0 to 255. As you move the sliders, the values are automatically entered in the Output Levels boxes. | |
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For information on using the eye dropper buttons to adjust the tonal range, see Adjusting the tonal range with the eyedroppers.