There are generally four main types of light sources for writing desk lamps: incandescent lamps, halogen lamps, fluorescent lamps and LEDs. Each of the four types of light sources has advantages and disadvantages. Different people may like the light color and brightness of different light sources. In order to project most of the light onto the table, the light source of the writing desk lamp is usually installed horizontally or downward. When buying a writing desk lamp, in addition to checking its optical performance, you should also check whether other performance is acceptable. One pull, two tunes, three shakes, four touches.