Airbrush professionals know that it cannot be used alone if the image is to achieve any serious realism: a good airbrush work would typically involve using brush, pencil, stencil knife, spatter, sponge, etc. etc. — all because the airbrush itself is good for reproducing only smooth gradients. It cannot handle other textures… primarily because it lacks a texture of its own. Its inherent texture is smooth, fine mist of paint droplets that is not discernible.

So does Photoshop.

Photoshop allows to apply color through use of the tablet by applying circular dabs of color along the path of the stylus. These can have different transparencies and different haziness of their edges; but they are always smooth and produce mathematially smooth color gradients. They even lack the finest minute grain of airbrush aerosol drops, which can be seen only with very close observation. they are perfect.

But painting media are never so perfect. They always have texture which comes as a side effect; it comes from the paper or canvas grain, from individual brush bristles, from uneven drying. It is precisely what airbrush lacks nearly and what Photoshop lacks completely. At first look it is easy to conclude that it is an unwanted side effect. In actuality, if you eliminate the side effect, you get that very “artificial look”. All the rest may be there, you could even paint the textures by hand, but it still will look unconvincing, as if the whole scene were made from the same material. Compare the different textures used on the same subjects to the unnaturally smooth airbrushed image.

	Airbrush
Dry bristle brush	Pastose oil	Crayon
Oil	Pointillism	Acrylic

The reason is that these “random”, emergent textures (called so because they may appear without special attention from the artist) are important for perception of the image They provide the necessary “detail”, actually “noise”, on the border of eye's perception, fooling the brain into believing that there is more detail than there is, and adding depth to the image. They “promise” more visual information than there really is; the brain does the rest.

Since the computer images inherently lack emergent texture, they lack “natural” look. Special effort is required to let emergent texture to appear and work its magic on the viewer. The rest of the article deals with methods of introducing it to computer art (provided that you aren't aiming at the polished but false airbrush look which has its uses, but is regrettably unapplicable in figurative art).

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