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Spatial and temporal effects of vision

The eye can function within a stimulus range of approximately 10⁻⁶ candela/square meter to 10° candela/square meter. The upper limit is determined by the risk that excessive radiation absorption will damage the retina. Although the eye cannot function effectively across the entire visible stimulus range simultaneously, it can still capture full information from the entire field of view by limiting the brightness range within the field of view to approximately 10⁴:1. This demonstrates that the eye is an optimally automated device, automatically adjusting vision to ensure maximum visual information, somewhat like an ammeter automatically selecting its current path to ensure its needle points to the appropriate reading on the scale. This adjustment, known as adaptation, takes time to complete. With sudden changes in field of view brightness, vision is weakened as it adapts to the new conditions