Compare the image shown here on the left, which has a gradual change from light to dark, with the image on the right, which clearly shows a sharp demarcation from light to dark.

• 比较显示的左侧的图像，它有一个从亮到暗的一个渐变的改变，在右侧的图像，它明显地在从亮到暗的地方有一个划分。