Brightness, also known as luminance, refers to how bright a light or an object looks to human eyes, that is, the level of “light”. When the surfaces of any two objects look equally bright, we can say that they have the same brightness. Since there are many factors affect brightness, it is not easy to measure. These include a smooth surface tending to look brighter than a rough surface in the same environment, so illumination is generally used as the basis for comparison. Illuminance refers to how much light (luminous flux) is received in a certain area. Simply speaking, it means “the brightness of the brightened place.” The unit for measuring illuminance is “Lux”. The higher the value, the brighter it is, and lower values indicate darker.
The level of illuminance has a huge impact on the reading situation. Research by the National Taiwan University of Science and Technology indicates that whether it is a hard copy or electronic ink, the eyes can recognize the text of the book more quickly and accurately in an environment with higher illuminance level. At the same time, smaller text font requires a higher level of illuminance. The level of illuminance has a more significant impact on the efficiency of reading when the text font is smaller.
When using consumer electronic products such as computers, tablets, mobile phones, etc., which have bright screens, if the ambient illumination is too low and has great contrast with the illuminance of the screen, it will easily cause glare. Although the study has not proven that glare will cause long-term damage to the eyes, it still makes the eyes tired and uncomfortable, and reduces efficiency at work indirectly. Therefore, use of consumer electronic products in an environment with insufficient illumination should be avoided.
And let's move to the question that people often ask, "how many lumens should a desk lamp have?" According to the definition of the American National Standard Practice for Office Lighting, when using a hard copy at work, the illumination must reach 500 Lux to meet the standard of “bright enough”, while the CNS standard recommends that the illumination of a study room at home should reach 750~1000 Lux to fulfill the suitability for writing and reading activities. In fact, everyone's subjective feelings of “bright enough” may be slightly different. Basically, adults need higher illumination than children to read text clearly.
It should be noted that for illumination, higher doesn’t mean better, and too high illumination will make people feel dazzled. However, in the case of a desk lamp, if the user feels it is too bright, the user can easily move the desk lamp to a farther away position. Usually, it is necessary to worry about insufficient illumination conditions.
There are no instruments to measure illuminance in general families, so, how can we know if it has reached the “bright enough” standard or not? Actually, it doesn't matter even there is no professional illuminance meter. Most desk lamps that are available on the market specify their level of illuminance in the detailed specifications. Usually, they are expressed in the form of “XX centimeters from the illuminated surface, the central illumination is XX Lux”. Users can take this information as a reference while purchasing desk lamps. For example: “40 centimeters from the illuminated surface, the central illumination is 1800 Lux” means that when the desk lamp is 40 centimeters away from the desktop, it can provide the center of the illuminated area of the desktop 1800 Lux. When it is “30 centimeters from the illuminated surface, the center illumination is 1200 Lux”, it means when the desk lamp is 30 centimeters away from the desktop, it can provide the center of the illuminated area of the desktop 1200 Lux. Some people are looking for the brightest LED desk lamp but you really have to consider your viewing habits and reading environment.
Before purchasing a desk lamp, you may measure the distance between the place where the desk lamp is planned to be located and the desktop. After the desk lamp is purchased, it is also recommended to install the lamp according to its illumination specifications. Of course, if you want to be 100% sure that the lighting environment of your home fulfills your requirements, you can also purchase an illuminometer to measure, thus protecting the health of the eyes of family members!