Continuous tone
A continuous tone image is one where each color at any point in the image is reproduced as a single tone, and not as discrete halftones, such as one single color for monochromatic prints, or a combination of halftones for color prints.
The most common continuous tone images are digital photographs every single pixel of which can take a continuous range of colors depending on the quantity of captured radiance. On the other hand, at a microscopic level, developed black-and-white photographic film consists of only two colors, and not an infinite range of continuous tones. For details, see film grain. Therefore, film is a halftone medium.