What factor decreases spatial resolution (SR) in imaging?

Increasing pixel size due to binning decreases spatial resolution because spatial resolution refers to the ability of an imaging system to resolve small details in the image. When binning occurs, multiple pixels are combined into one larger pixel. This can enhance signal strength or improve the signal-to-noise ratio, but it sacrifices the fine detail that smaller pixels can capture. Consequently, larger pixels mean that the imaging system has a reduced capacity to distinguish between closely spaced objects, leading to a loss in image clarity and detail, which is precisely what spatial resolution measures.

In relation to the other options, while overexposure to light, lower density illumination, and optical aberration of lenses can all have negative effects on image quality, they do not directly relate to spatial resolution in the same manner as pixel size changes. Overexposure might lead to image blurring or saturation, lower illumination density could result in a darker image that is harder to interpret, and optical aberrations can distort the image but do not specifically pertain to the inherent capability of resolving fine details as much as pixel size does. Thus, the hallmark of decreased spatial resolution is notably associated with increased pixel size due to binning.