Which of the following is a common artifact found on radiographic images?

Motion blur from patient movement during exposure is indeed a common artifact found on radiographic images. This artifact typically occurs when the patient does not remain still during the imaging process, causing the captured image to appear smeared or distorted. Such motion can result in a lack of clarity and definition in the anatomical structures being examined, leading to difficulties in interpretation.

The other answer choices describe scenarios that are less representative of common artifacts. For example, darkening of the entire image may occur due to overexposure but is not as frequent as motion blur, which is directly related to patient behavior during the imaging process. A clear depiction of all structures is the desired outcome of a radiographic image and is not considered an artifact; instead, it represents optimal imaging quality. Lastly, while brightness increase due to film aging can occur, it is not as prevalent as motion artifacts caused by patient movement, which make it a more significant concern in routine imaging practice.