A good light by illumination, brightness, glare, shadows, color, stability factors and constraints. (1) illumination. Is accepted luminous flux per unit area. (2) the uniformity of the illuminance. (3) The brightness distribution. Glare control (4). (5) the color rendering properties of the light source. Bright and concise. And decoration style match up better. There are also try to be energy-efficient, not more light, the brighter the better.