First, the display screen on a sunlight readable/outdoor readable LCD should be bright enough so that the display is visible in direct or strong sunlight. Second, the display contrast ratio must be maintained at 5 to 1 or higher.
Although a display with less than 500 nits screen brightness and a mere 2 to 1 contrast ratio can be read in outdoor environments, the quality of the display will be dreadfully poor and not get the desired information across effectively. A true sunlight readable display is normally considered to be an LCD with at least 1000 nits of screen brightness and a contrast ratio greater than 5 to 1. In outdoor environments under the shade, such a display can provide an excellent image quality.