Final answer:
In radiographic imaging, the primary factor controlling density is kilovoltage (kVp), as it determines the energy of X-ray photons which affects material penetration and consequently the image density.
Step-by-step explanation:
The density in the radiographic image is primarily controlled by the milliamperage (mA), kilovoltage (kVp), exposure time, and source-to-image distance (SID). However, if we were to choose the primary controller among these, the kilovoltage (kVp) stands out because it dictates the energy of the X-ray photons, which in turn determines the ability of the X-rays to penetrate the subject matter. A higher kVp means higher energy photons that can penetrate denser materials, resulting in areas of less density on the radiographic image. Alternatively, a lower kVp would result in X-ray photons with less energy, increasing the absorption by denser materials and therefore increasing the density observed on the radiographic image.