Improving Dark Images
Try this: Open any grayscale image you think is too dark (I'll show you how to work with color in a minute), like the one shown in Figure 6.30. Next, choose Image > Adjustments > Curves, and add a point by clicking the middle of the line. Pull the line straight down, and see what happens to your image (Figure 6.31). Compare the curve with the gradient at the left of the Curves dialog box. The farther you move the curve down, the less ink you use and therefore the brighter the image becomes. If part of the curve bottoms out, the shade represented by that area becomes pure white because there will be no ink used when the image is printed.
Figure 6.30. Start with a dark grayscale image. (©2005 PhotoSpin, www.photospin.com)
Figure 6.31. Move the curve down to reduce how much ink is used.
Any part of a curve that's below the original line indicates an area that is using less ink, which means that it has been brightened. Look at the gradient directly below those areas to determine which shades of the image were brightened (Figure 6.32). The farther the line is moved down from its original position, the brighter the image will become (Figure 6.33).
Figure 6.32. Comparing the curve with the gradients.
Figure 6.33. To figure out how much ink you've removed, look below where the line used to be.
Previewing the Changes
You can compare the original and changed versions of the image by checking or unchecking the Preview check box. As long as the check box is unchecked, you'll see what the image looked like before the adjustment. When you click to check it, you'll see the changes you just made.