Sehschwelle

Sehschwelle refers to the minimum intensity of light that can be detected by the human eye. It is a psychophysical concept, meaning it relates subjective experience to objective physical measurement. This threshold is not a fixed value but varies depending on several factors, including the duration of the light stimulus, the size of the area being stimulated, the wavelength of the light, and the state of the observer's adaptation to light levels.

The absolute threshold of vision is typically defined under optimal conditions, such as in a dark-adapted eye viewing a brief flash of light in the periphery of the visual field. Under these circumstances, the human eye is remarkably sensitive, capable of detecting individual photons. However, in everyday situations, the effective sehschwelle is higher due to a combination of less-than-ideal conditions.

The concept of sehschwelle is crucial in fields like vision science, optometry, and lighting design. It helps researchers understand the limits of human visual perception and how different lighting conditions affect our ability to see. For instance, in designing lighting for public spaces or workplaces, knowledge of the sehschwelle informs the required illumination levels to ensure adequate visibility without causing discomfort or strain. It is a fundamental parameter for understanding the sensitivity and limitations of our visual system.