occurs when a gradual or smooth tonal transition in an image appears or is made to appear as an abrupt change from one tone to another. Digitally, it can be achieved by limiting the number of colors in an image so that the change from one tone to another is sudden, rather than continuous and gradual. Posterization can be noticed, for example, in an image that has a relatively large area of color that appears banded where the tonal changes should instead appear to be gradual.
A photographic or digital graphic effect arising from reducing the number of continuous tones in an image. Can be a deliberate effect or a result of over-manipulation or compression in a digital image.
The display of "bands" of color rather than a true gradient. Sometimes called "false contouring" it is typical a function of inadequate contrast ratio. Makes colored gradients appear as a series of "rings", with large changes in color between the rings as opposed to gradual, "gradient" changes.