What is the name of the input-output curve used to express the change in film density with changes in radiographic dose, and is also referred to as the H&D curve?

• A. H&D Curve
• B. Characteristic Curve
• C. Sensitometric Curve
• D. Exposure-Density Curve

Answer: (B)

The main concept is the film’s response to exposure, shown as a curve that relates image density to the amount of exposure. This input-output curve plots optical density on the y-axis against log exposure on the x-axis, illustrating how the film responds as you increase dose. This curve is commonly known as the characteristic curve. It’s also referred to as the sensitometric curve and is the same as the Hurter-Driffield (H&D) curve. Naming it the characteristic curve is standard in radiography because it emphasizes the film’s inherent response behavior. While other labels describe the same relationship, the characteristic curve is the most conventional term used to capture this input-output behavior, including its toe, linear portion, and shoulder that relate to speed and contrast.