A portable electronic device may include a display for displaying an image having different color or grey scale fields. Neighboring fields in the image may have different luminance. The portable electronic device may also include an ambient light detecting unit and a control unit. The control unit receives a luminance value corresponding to detected ambient light from the ambient light detecting unit, compares the luminance value with an ambient light level threshold and increases the difference in luminance between neighboring fields of an image being displayed by the display when the luminance exceeds the ambient light level threshold.