The mesopic vision is a vision intermediate (intermediate between the photopic and scotopic ) that occurs in situations of illumination , which without reaching total darkness, not become the light of day in the sun. It is mainly the type of vision used in artificial lighting conditions, where both cones and canes come into play.
The human visual system has two types of receptors in the retina , rods and cones, which used to send visual signals to the brain. The current photometric system to determine the amount of light needed to perform a task, regardless of lighting conditions or time of day, is based on how the cones work. Cones are the dominant visual receptors under photopic lighting conditions (during the day). The rods function mainly under dark conditions (escotopicos). Under the conditions of mesopic lighting , typically found outdoors at night, the combination of rods and cones are part of the human visual function. Therefore outdoor luminaires which are adjusted according to the way human vision behaves under conditions of mesopic lighting , can be used to reduce glare from the surface of the streets and at the same time provide better visibility. 1
Most night scenes and exterior lighting road are in the mesopic range. 2
The traditional method of light measurement considers only photopic vision and is commonly inaccurate in predicting how humans perceive light at night. Research in this area typically focuses on improving exterior lighting as well as lighting for aviation. The visual effect considers the measurement of mesopic lighting and is used for testing outdoor lighting fixtures and street lighting.
- Back to top↑ Peter Morante (2008). „Mesopic Street Lighting Demostration and Evaluation, Final Report“. Lighting Research Center, Rensselaer. Pg 1-2
- Back to top↑ CIE Publication No. 41. Light as a visual true quantity: principles of measurement. 1978.