Final answer:
Focal-spot size does not have an impact on radiographic contrast. It is related to the sharpness and resolution of the image. Factors like photon energy, grid ratio, and OID, however, do affect radiographic contrast.
Step-by-step explanation:
The question pertains to radiographic contrast, which is the degree of differentiation between the dark and light areas on a radiograph. Radiographic contrast is influenced by several factors, including:
- Photon energy: Higher energy photons produce lower contrast due to increased penetration, while lower energy photons yield higher contrast.
- Grid ratio: A higher grid ratio reduces the amount of scatter radiation reaching the image receptor, thus enhancing contrast.
- Object-to-image distance (OID): Greater OID can increase contrast by reducing the amount of scatter radiation.
The factor that does not impact radiographic contrast is focal-spot size. Focal-spot size influences the sharpness and spatial resolution of the radiograph rather than its contrast. Therefore, the answer is D. Focal-spot size.