A brightness tester is an instrument designed to measure and quantify the intensity of light or brightness in various settings. It typically uses sensors or photodetectors to assess the luminance or brightness levels in lux or other relevant units. These devices are commonly used in quality control, research, and industrial applications to ensure consistent lighting conditions or to assess the performance of displays, screens, and lighting systems. Brightness testers play a crucial role in maintaining standards and visual comfort in environments where lighting quality is essential.