What does the 6500k written on the energy-saving light bulb mean?

Indicates the color temperature of the lamp.

Explanation:

Literally speaking, energy-saving light bulb is a kind of light source that saves more electricity than traditional incandescent lighting. It is made of tricolor phosphor irradiated by 254nm ultraviolet light, and its efficiency of converting electric energy into light energy is higher than that of incandescent lamp.

The color temperature calibrated by this method is just the opposite of what the general public thinks is "warm" and "cold". For example, people usually think that red, orange and yellow are warmer, while white and blue are colder. In fact, the color temperature of red is the lowest, and then gradually increases to orange, yellow, white and blue, and blue is the highest color temperature.

Extended data:

When shooting in natural light, because the color temperature of light is different in different time periods, the color of the photos taken is also different. For example, when shooting under a clear blue sky, the color temperature of the light is high, and the photo is cold; But if you shoot at dusk, the color temperature of the light is low, so the photo is warmer. When shooting with artificial light, there are also different types of light sources, and the colors of the photos taken are different.

Understanding the relationship between light and color temperature is helpful for photographers to shoot under different light, calculate in advance what color tone photos they will take, and further consider whether to strengthen or weaken this color tone, and which function of the camera should be used to strengthen or weaken this color tone in actual shooting.