An example of a photo in JPEG
format (24bit colour or 16.7 million colours) before posterization, constrasting the result of saving to GIF
format (256 colours). Posterization occurs across the image, particularly obviously in areas of subtle variation in tone.
Posterization occurs when a region of an image with a continuous gradation of tone is replaced with several regions of fewer tones, resulting in an abrupt change from one tone to another. This creates an effect somewhat similar to that of a simple graphic poster. Image File history File linksMetadata Download high resolution version (658x894, 241 KB) Summary The following is an example of a scenario where posterization may occur, and relates to the image above. ...
Image File history File linksMetadata Download high resolution version (658x894, 241 KB) Summary The following is an example of a scenario where posterization may occur, and relates to the image above. ...
A photo of a flower compressed with successively lossier compression ratios from left to right. ...
GIF (Graphics Interchange Format) is a bitmap image format for pictures that use 256 (or fewer) distinct colors (though there is a workaround for this limitation) and animations that use 256 (or fewer) distinct colors per frame. ...
1942 US government war poster. ...
Posterization can also be achieved digitally in most photo-editing programs
Definition: a process in photograph developing which converts normal photographs into an image consisting of distinct but flat areas of different tones or colors. A posterized image often has the same general appearance, but replaced by abrupt changes in shading and gradation from one area of tone to another. Printing posterization from black and white requires density separations, you than print them on the same piece of paper to produce types of images on the facing page. Separations can be made by density, or color through different exposures. Density Separations can be achieved by printing three prints of the same picture at different exposure times.
Black and White
step 1: project the original image, leaving a wide margin for registration holes
step 2: position a sheet of lith film, test exposure, process
step 3: do the same process with three different exposure times
step 4: cut pin holes in the marigins of each print
step 5: combine them with pins
step 6: try switching around the order of the prints until you achieve the posterized look you were going for
psuedo-posterization this type of posterization has similar results to regular posterization however, you use just one sheet of high-contrast film. You then set the enlarger to the size you desire, and test print (so that shadows detail fills in) secondly you underexpose the image on lith film. Finally you place the processed film over bromide paper and expose them to light from the enlarger.
External links and sources
Source:' Langford, Michael. The Darkroom Handbook. New York: Dorling Kindersley Limited, 1981. 245-249.