Posterisoituminen

Posterisoituminen, also known as posterization or solarization, is an effect in photography and digital imaging where the tonal gradations of an image are reduced, resulting in a stark, poster-like appearance. Instead of smooth transitions between light and dark areas, posterization creates distinct bands of color or tone. This effect is achieved by limiting the number of available tones in the image.

In traditional analog photography, posterization could be achieved through special developing techniques or by using lithographic film, which has a very high contrast, to create intermediate positive and negative masks. These masks were then combined to produce an image with limited tonal range. Digital software, however, provides a much more straightforward method. By adjusting the number of "levels" or "steps" in an image's color or grayscale information, a posterized effect can be simulated. Reducing these levels effectively collapses continuous gradients into discrete steps.

The visual outcome of posterization can vary depending on the number of levels chosen. A high number of levels might result in a subtle reduction of gradations, while a very low number can create a graphic, almost abstract look with large, flat areas of color. Posterization is often used as an artistic effect to achieve a specific visual style, highlighting shapes and outlines rather than subtle tonal variations. It can be applied to both color and black-and-white images.