Photography of the fluorescence produced by ultraviolet illumination uses visible wavelengths of light. This differs from Sabbath candles which are meant to be used for illumination and lighting. Phong reflection is an empirical model of local illumination. Photographs made of various dyes that fluoresce under ultraviolet illumination are also useful. This effect introduces a difference in color contrast under different levels of illumination. The headlights were also equipped with a programmable delay feature for proximity illumination. The fixed output varies with the overall illumination of the sky. Many reticle illumination and pattern options are available. This separation helps the motion detector to discriminate between field-wide illumination and moving objects. Lidar uses active sensors that supply their own illumination source. Electromagnetic warning against radar illumination is also installed. The maximum power point of a photovoltaic varies with incident illumination. They allow momentary illumination of a target. Cube maps can be useful for modelling outdoor illumination accurately. Watches that incorporate batteries often have the electric illumination of their displays.