Which parameter primarily affects image sharpness in radiography?

In radiography, the parameter that primarily affects image sharpness is the Source-to-Image Distance (SID). Increasing the SID can enhance image sharpness due to the geometric factors involved in radiation exposure. When the distance between the radiation source (the X-ray tube) and the image receptor (film or digital detector) is greater, the radiation diverges less as it travels to the detector. This reduced divergence minimizes the penumbra effect, which is the blurring at the edges of structures and enhances the definition of the image, resulting in sharper images.

While parameters such as film speed, mAs (milliamperes-seconds), and kVp (kilovolt peak) also play significant roles in imaging, they primarily affect aspects such as exposure and contrast rather than sharpness. Film speed determines sensitivity to radiation, mAs controls exposure quantity, and kVp pertains to the energy of the X-rays generated. Therefore, while these factors are important for overall image quality, they do not directly correlate with the sharpness achieved as significantly as SID does.