Images which have a step less tonal gradation (or the ability to have one) from white to black. The opposite to this is half tone images where the image is made up of dots produced by a dot screen. Images reproduced with commercial offset printing techniques are not continuous tone but half tone images.
Photographic image that shows a continuous density range between the lighter and darker areas without screening dots. when bombarded with an electron beam from a cathode ray tube (CRT). Each pixel on the screen or monitor consists of a triad of phosphor dots, one emitting red light, one emitting green light and one emitting blue light. The CRT can turn on different combinations of phosphor dots to create intermediary colors, and can vary the intensity of the electron beam to produce hues with more or less saturation.
A photographic image, which has not been screened and contains gradient tones, eg a normal photograph.