Adobe PHOTOSHOP CS2 User Manual page 22

ADOBE PHOTOSHOP CS2 14
User Guide
2. Create a new Levels adjustment layer.
Choose Layer > New Adjustment Layer > Levels and click OK in the New Layer dialog box. Rather than working
directly on the image, we are going to make the tonal correction in an adjustment layer. Working in an adjustment
layer leaves the original image untouched so you can discard your changes and restore the original image at any time.
3. Evaluate the image histogram.
The histogram in the center of the Levels dialog box shows how pixels are distributed in an image by graphing the
number of pixels at each intensity level. It displays the relative number of pixels in the shadows (left part of the
histogram), midtones (middle), and highlights (right). You can see that this image is not using the entire tonal range.
Pixels don't extend across the entire length of the histogram.
4. Set the shadows and highlights.
Move the black point input slider and the white point input slider (the black triangle and white triangle located
directly beneath the histogram) inward from the edges of the histogram. The black point input slider adjusts pixels
to value zero. All pixels at the level you set and any pixels below become black in the image. The white point input
slider maps values at its position or above to 255, or pure white. After you adjust the sliders, the image will have more
contrast.