What is Brightness? What are Its Impacts?

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 that 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 lit up place.” The unit for measuring illuminance is “Lux”. The higher the value, the brighter it is, and lower values indicate darker areas or spaces.

The level of illuminance has a huge impact on reading. Research by the National Taiwan University of Science and Technology indicates that whether it is hard copy or electronic ink, our eyes can recognize text in a book more quickly and accurately in an environment with higher illuminance levels. At the same time, a 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, and mobile phones, which all 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 eyes, it still makes 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.

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 hard copy at work 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 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 only necessary to worry about insufficient illumination conditions.