At which wavelength is there an equal sensitivity point for photopic and scotopic systems?

The equal sensitivity point for photopic (daylight vision) and scotopic (night vision) systems is at approximately 498 nm, which is close to 500 nm. This point reflects where both systems have similar sensitivity to light, even though they operate under different lighting conditions and with different photoreceptor cells. The photopic system relies on cone cells and is more sensitive to longer wavelengths, while the scotopic system utilizes rod cells and is better suited for low-light environments.

Around the equal sensitivity point, both systems exhibit a similar response to light, indicating that the transition from scotopic to photopic vision occurs in this region of the spectrum. Therefore, the wavelength identified as approximately 500 nm is associated with the overlap in sensitivity for both visual systems, rather than a wavelength like 650 nm or higher, where only the photopic system would respond effectively.

This understanding emphasizes the different operational ranges and sensitivities of the photopic and scotopic visual systems under varying lighting conditions.