Technique 30 shows you how to adjust the tone and color of an image using Levels.
The color cast of this great photograph of Mount Banner (top) is a little dark, the snow isn’t as white as it should be, and the sky could be more blue.
I could have adjusted the tone and color by using Auto Levels, which tends to work well generally, but because this photo is so special, I really wanted to adjust the colors by hand.
After opening the Levels dialog box, I started by choosing the Red channel and adjusting the highlights and midtones using the histogram (middle left). Next, I chose the Green channel and adjusted its highlights and midtones as well (middle right). Finally, I selected the Blue channel and adjusted the midtones and highlights to create a lovely blue sky (bottom).
Original image Harold Davis.