Perhaps the best way to understand the concepts of Pictoralism, Modernism and Post modernism is by comparison. Historically pictoralism was popular in photography from the late 1800’s until around the 1920’s, Modernism from 1920’s until around the 1950’s and post modernism from the 1950’s onwards. Each movement rejected the main tenants of it’s predecessor.
Pictorialism refers to a style in which the photographer has somehow manipulated what would otherwise be a straightforward photograph as a means of “creating” an image rather than simply recording it. Typically, a pictorial photograph appears to lack a sharp focus (some more so than others), is printed in one or more colors other than black-and-white (ranging from warm brown to deep blue) and may have visible brush strokes or other manipulation of the surface. For the pictorialist, a photograph, like a painting, drawing or engraving, was a way of projecting an emotional intent into the viewer’s realm of imagination. (Source Wikipedia)
Think clean, hard lines, lots of depth of field – everything in those photos is in focus. Sharp edges, straight, parallel lines- technical perfection. Modernism rose during the late WWII and post war era. It reflects the social desire for conformity, for solidity and stability. Modernism rejected the conventions of Pictoralism that preceeded it.
Post-modernism rejects technical perfection solely for its own sake (an absolute mortal sin in here!) and seeks to show parallel narratives for its’ subjects. Reality is not what it seems, and the artist attempts to show you that on many levels within the shot. Technical work is often done badly on purpose, as a rejection of modernist academia. Appropriation and repurposing of earlier images, mixing media, using media not traditionally associated with the finished imagery i.e. sculpture incorporating photography, and playing with scale.
source (Yahoo Answers)