What does peak sensitivity refer to in the context of luminous efficiency?

Peak sensitivity in the context of luminous efficiency refers to the maximum light sensitivity at specific wavelengths. This concept is important because it highlights how the human eye perceives brightness at different wavelengths of light. The photopic (daylight) sensitivity of the human visual system peaks around 555 nanometers, which corresponds to green light. At this wavelength, the eye is most efficient in converting light into perceived brightness.

Understanding peak sensitivity helps explain why certain colors or wavelengths appear brighter than others to the human eye, despite having the same measurable intensity. It also informs many practical applications, such as lighting design, display technology, and vision science, as it considers how the eye responds to different light conditions and colors. This understanding enhances various fields, from photography to environmental lighting standards, ensuring optimal visibility and comfort in visual environments.