The absolute value of picture making is that it is always cultural and always of its time. Great art, or at least best efforts, provide valuable insight into the intellectual capacity of people far distant from us. Pretty much all painting was representational prior to the 1940's, which makes for a convenient yardstick to judge the relative merits of various periods and individuals against the whole.
The learning curve to becoming a realist painter is as it always has been (and believe me it can take years). In a sense too the materials have remained much the same, paint, canvas/board, pencil and paper. With that, it's of interest that art's great dramas, the renaissance, impressionism, et al. are often tied to innovative changes to these basic materials.
In Europe until the end of the 14th. century fresco (colored plaster paint) and tempera (pigment in egg yolk and water) were the standard. Both needed an inflexible surface to remain viable, the former walls and the latter usually wooden boards.
Generally speaking Jan Van Eyck is credited with inventing oil painting around 1410. The wisdom then was that these works were inferior in every way to tempera painting, but within a generation or so the vastly superior qualities of oils became widely appreciated. This opened the door to Leonardo Da Vinci and the Italian Renaissance that followed.
The process of painting, regardless of the medium, was laborious. Pigments that came from all corners of the known world needed to be sourced and a supply maintained. Every day paint had to be ground fresh. Studio assistants, often apprentices, were vital to the tasks of picture making. And so it was until the 19th. century, paintings took time, unwieldy equipment and manpower to produce, artists were thus tied to their studios. Paintings themselves however, regardless of size suddenly became portable thanks to the flexible nature of oil paint and the advent of canvas.
Modern paint generally consists of the pigment (color), binding agent (oil, etc.) and a suspending agent to maintain a consistent texture and prevent the pigment and binder from separating. Ready made paints first became available during the early 19th. century with the introduction of pig bladder containers, and in complement industrial paint manufacturing began then also.
In 1841 John G. Rand invented the revolutionary zinc tube, followed by the discovery, in the 1850's, of suspending agents that would keep the paint a consistent texture almost indefinitely. With portable, resealable colors artists were suddenly free to travel along with the tools of their trade. This set the stage for the next upheaval, Impressionism.
It didn't take long for these innovations to manifest themselves. Within a decade the Impressionist painters had evolved a "radical" new look to their work. This early modern art is at least as much opportunism as genius and probably inevitable from the moment tube paints hit store shelves. The idea that photography alone is responsible for the demise of classical painting is nonsense. The post Impressionist possibility that pictures no longer needed to be literal opened the door to an examination of the elements that compose a classical painting, color: Fauvism, and the line: Cubism. Many of the movements that follow (expressionism, abstraction, etc.) are lesser offshoots of the initial deconstruction of realism.
