In digital radiography, what term describes the digital equivalent to density or the overall degree of image darkening?

• A. Brightness
• B. Contrast
• C. Exposure
• D. Resolution

Answer: (A)

In digital radiography, the overall darkness or lightness of an image is described by brightness. This is the digital counterpart to the traditional density on film, but it refers to the range of pixel values displayed across the entire image. When brightness is increased, all pixel values are shifted to lighter grayscale levels, making the image look lighter; when brightness is decreased, the image becomes darker.

This global adjustment is different from contrast, which deals with the difference between light and dark areas (the range of grayscale values) and is usually controlled separately, such as with window width settings. Exposure concerns how much radiation actually reaches the detector and influences image quality and dose, but it doesn’t define how dark or light the displayed image appears. Resolution is about the level of detail or sharpness in the image, not its overall darkness.

Clinically, brightness is what you manipulate to optimize visibility after acquisition, while keeping appropriate contrast and exposure for diagnostic needs.