What happens to sensitivity as illumination decreases?

As illumination decreases, the functionality and sensitivity of visual receptors in the retina adapt to the changing light conditions. Rods, which are highly sensitive to low light levels, become more active as light diminishes, allowing us to detect faint light and perceive shapes and movements in dark environments. This enhances sensitivity in low-light conditions, where the cones, which are responsible for color vision and function best in bright light, have reduced activity. Therefore, while sensitivity increases primarily in rods under low illumination, the overall sensitivity of our night vision improves as the rods take over the role of light detection.

Cones, on the other hand, do not increase in sensitivity in low light; they are adapted for bright conditions. The term "sensitivity" in this context primarily applies to how well our visual system can respond to light stimuli as environmental illumination changes. Thus, the notion that sensitivity increases for both rods and cones fails to recognize the distinct roles these photoreceptors play under varying illumination conditions.

In bright light scenarios, cones operate at their peak sensitivity, while rods are disengaged. As light diminishes, sensitivity specifically in rods increases, allowing better vision in dark settings while cones are less effective. Therefore, the correct understanding is that sensitivity increases predominantly in rods,