In lighting design, it is necessary to consider the floodlight characteristics of the object surface
The reaction of an object surface to incident light is not only affected by the color and cleanliness of the surface, but also depends on whether the surface is rough or mirrored, deep-textured or patterned. Mirror-reflecting surfaces, such as glass, gold foil, aluminum, stainless steel, mosaic tiles (i.e. small ceramic tiles), glazed tiles, etc., are particularly unsuitable for floodlighting. During the day, the main light source comes from the sky above the building, which is reflected into the eyes of the observer through the mirror, making the surface look shiny. But at night, the lighting is installed on the ground, and the direction of the main light source is opposite. The light emitted by the mirror is directly reflected into the air, away from the observer's eyes, making the surface look dim and lifeless, losing the beauty shown during the day.
For buildings with gold-leaf-finished spires, if the tower surface is decorated with horizontal ribs to reflect the light downward, a good floodlighting effect can be obtained. For all mirror-reflecting surfaces, the luminous efficiency depends mainly on the brightness of the light source, not the illumination, and also varies with the viewing direction.
Regardless of the reflective properties of the surface, floodlighting cannot make a building or illuminated object appear the same as it does during the day, because the main light source is usually in the opposite direction, and the scattered light from the sky during the day is difficult to imitate. Therefore, the best decorative floodlighting should try to take advantage of this difference, rather than reduce it. For industrial lighting or other floodlighting with strict functional requirements, the difference between natural and artificial lighting is not a disadvantage. For example, floodlighting in sports venues is mainly to enable spectators to focus their attention. Carefully arranged floodlights in construction sites and refineries can increase visual attention. For example, the tracks of railway freight assembly yards are painted white on the stone masonry at the edge of the dock or the curb, which will also be clearer than installing supplementary floodlighting.