In imaging, what is the effect of reducing SOD?

Reducing the Source-to-Object Distance (SOD) in imaging results in increased magnification of the object being imaged. Magnification occurs because the closer the source of radiation (such as an X-ray tube) is to the object (such as a patient's anatomy), the larger the image appears on the detector or film. This is due to the geometric properties of how light and radiation travel. As the SOD decreases, the angles at which the rays intersect the object increase, leading to a larger projected image size.

In clinical practice, increased magnification can be beneficial for viewing fine details of small structures, but it can also lead to a decrease in image sharpness (resolution) if the increased size is not compensated for with appropriate imaging techniques or adjustments. However, the primary effect of reducing the SOD is indeed an increase in magnification.