Which factor is NOT affected by the focal spot size in radiography?

The factor that is not affected by the focal spot size in radiography is image contrast. Image contrast primarily refers to the difference in density between adjacent areas on a radiographic image, which is primarily determined by the technical factors used during exposure (such as kVp and mAs), the characteristics of the film or digital detector, and the properties of the tissue being imaged.

Focal spot size primarily influences the sharpness of the image and spatial resolution, as a smaller focal spot size reduces the penumbra effect and enhances image detail. However, while spatial resolution and image sharpness improve with a smaller focal spot, the inherent contrast of the image is maintained by other technological and biological factors. Thus, the focal spot size does not play a direct role in altering the contrast of the image.