Any part of the curve that's flatter (more horizontal) than the original line indicates an area where the contrast has been reduced (shades of gray become more similar). Look at the gradient directly below these areas to determine which shades of the image were changed. The flatter the line becomes, the less contrast you'll see in that area of the image. When you lower the amount of contrast in an image, it becomes harder to see detail. This can be useful if you want detail to be less visible. If the curve becomes completely horizontal in an area, you've lost all detail there (Figures 6.41 to 6.43). Remember, it's a bar chart—the same height means the same brightness.