<prompt> Characteristic curve is:A plot of relationship between film optical density and exposureA plot of relationship between contrast and exposureA plot of relationship between film optical density and contrastA plot of relationship between film latitude and radiographic density  <response>: Characteristic curve:A plot of the relationship between film optical density and exposure is called a characteristic curve. It usually is shown as the relationship between the optical density of the film and the logarithm of the corresponding exposure. As exposure of the film increases, its optical density increases. 