Which law quantifies the slope in region 2 of a light adaptation curve?

The DeVries-Rose Law quantifies the slope in region 2 of a light adaptation curve. This law describes how our visual system adapts to changes in light intensity, specifically how the threshold for detecting changes in light intensity varies as background illumination increases. It is particularly relevant in understanding the relationship between stimulus intensity and the perceived change in brightness under different lighting conditions.

In the context of light adaptation, region 2 refers to a range of light levels where the visual system’s sensitivity is adjusting, and the DeVries-Rose Law provides a mathematical expression for the relationship between light intensity and perception during this adaptation process. This principle illustrates that as illumination increases, the amount of change needed to perceive a difference also increases, aligning with the logarithmic nature of human visual perception.

Other laws mentioned, such as Weber's Law, focus more on the ratio of change needed for perceiving differences, while the Dowling-Rushton Law and Rico's Law pertain to different aspects of visual performance and don’t specifically describe the adaptation curve. Therefore, the DeVries-Rose Law is the most accurate representation of the phenomenon occurring in region 2 of the light adaptation curve.