When a small light source is brought close to an object, it can create the perception that everything around it becomes darker. This effect is known as "simultaneous contrast" or the "contrast effect."
The human visual system is highly sensitive to contrasts and differences in light intensity. When a bright light source, such as a flashlight, is brought close to an object, it increases the local contrast between the illuminated area and the surrounding regions. This heightened contrast can cause the surrounding areas to appear relatively darker in comparison.
Additionally, the human eye has a limited dynamic range, which means it can only perceive a certain range of brightness levels at once. When a bright light is introduced in close proximity, it can temporarily saturate the visual system, making the surrounding areas seem darker in contrast.
Moreover, the phenomenon of "adaptation" plays a role. Our eyes continuously adjust their sensitivity to the ambient light levels. When a bright light is introduced, the eyes adapt to the increased brightness, causing the surroundings to appear darker when the light source is removed.
Overall, the combination of contrast effects, dynamic range limitations, and adaptation processes in the visual system contribute to the perception that everything around a small, close light source appears darker.