"Mode" change occurs by varying the relative amounts backlight and ambient light. With more backlight, a higher chrominance is available and a color image display is seen. As ambient light levels, such as sunlight, exceed the backlight, a grayscale display is seen; this can be useful when reading e-books for an extended time in bright light such as sunlight. The backlight brightness can also be adjusted to vary the level of color seen in the display and to conserve battery power.