The viewing angle is the angle at which the image quality of an LCD degrades and becomes unacceptable for the intended application. Viewing angles are usually quoted in horizontal and vertical degrees with importance dependent on the specific application. As the observer physically moves to the sides of the LCD, the images will degrade in three ways. First, the luminance drops. Second, the contrast ratio usually drops off at large angles. Third, the colors may shift. Most modern LCD’s have acceptable viewing angles even for viewing from the sides.
For LCD’s used in outdoor applications, defining the viewing angle based on CR alone is not adequate. Under very bright ambient light conditions the display is hardly visible when the screen luminance drops below 200 nits. Therefore, the viewing angles are defined based on both the CR and the Luminance.