An illustration is a visualization or a depiction of a subject made by an artist, such as a drawing, sketch, painting, photograph, or other kind of image of things seen, remembered or imagined, using a graphical representation. The word comes from the latin word illustra'tio, illu'stro meaning enlighten, irradiate. Printing is the current process for reproducing illustrations, typically with ink on paper using a printing press. Illustrations can be artistic images illustrating for example a text, poem, fashion, magazines, stamps or a book and very often illustrations were made for children's books. The aim of an illustration is to elucidate or decorate a story, poem or piece of textual information by providing a visual representation of something described in the text. Illustrations can also represent scientific images of flora, medicine or different processes, a biological or chemical processes or technical illustrations to give information on how to use something. Illustrations can be executed in different techniques, like watercolor, gouache, ink, oil, charcoal chalk or woodcut.
Illustrations are often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing.
Medieval codices' illustrations were called illuminations. Johannes Gutenberg invented the printing press and independently developed a movable type system in Europe, along with innovations in casting the type based on a matrix and hand mould. He also added illustrations to his printed books, usually woodcuts. During the 15th century, books illustrated with woodcut illustrations became available. The main processes used for reproduction of illustrations during the 16th and 17th centuries were engraving and etching. At the end of the 18th century, lithography allowed even better illustrations to be reproduced. The most notable illustrator of this epoch was William Blake who rendered his illustrations in the medium of relief etching.
Early to mid 19th Century
Notable figures of the early century were John Leech, George Cruikshank, Dickens' illustrator Hablot Knight Browne, and, in France, Honoré Daumier. The same illustrators contributed to satirical and straight-fiction magazines, but in both cases the demand was for character-drawing that encapsulated or caricatured social types and classes.
The British humorous magazine Punch, which was founded in 1841 riding on the earlier success of Cruikshank's Comic Almanac (1827–1840), employed an uninterrupted run of high-quality comic illustrators, including Sir John Tenniel, the Dalziel Brothers, and Georges du Maurier, into the 20th century. It chronicles the gradual shift in popular illustration from reliance on caricature to sophisticated topical observations. These artists all trained as conventional fine-artists, but achieved their reputations primarily as illustrators. Punch and similar magazines such as the Parisian Le Voleur realised that good illustrations sold as many copies as written content.
Golden age of illustration
The American "golden age of illustration" lasted from the 1880s until shortly after World War I (although the active career of several later "golden age" illustrators went on for another few decades). As in Europe a few decades earlier, newspapers, mass market magazines, and illustrated books had become the dominant media of public consumption. Improvements in printing technology freed illustrators to experiment with color and new rendering techniques. A small group of illustrators in this time became rich and famous. The imagery they created was a portrait of American aspirations of the time. 
Technical illustration is the use of illustration to visually communicate information of a technical nature. Technical illustrations can be component technical drawings or diagrams. Technical illustration in general aim "to generate expressive images that effectively convey certain information via the visual channel to the human observer". Nowadays, many illustration programs are used to create technical illustrations due the need for detailed imaging and repeated updating. Besides the commonplace 2-D Adobe Illustrator, there are many 3-D computer graphics software that are often utilized to create illustration for textbooks, especially scientific ones. Technical illustrations generally describe and explain the subjects to a nontechnical audience. Therefore the visual image should be accurate in terms of dimensions and proportions, and should provide "an overall impression of what an object is or does, to enhance the viewer's interest and understanding".
Today, there is a growing interest in collecting and admiring original artwork that was used as illustrations in books, magazines, posters, blogs, etc. Various museum exhibitions, magazines and art galleries have devoted space to the illustrators of the In the visual art world, illustrators have sometimes been considered less important in comparison with fine artists and graphic designers, the term "illustrative" sometimes being used as a negative critique. But, possibly in part due to the growth of video game and graphic novel industries, as well as a recent swing in value towards illustration in magazines and other publications over photography, illustration is becoming a valued, popular, and profitable art form that can acquire a wider market than the other two, such as in Korea, Japan, Hong Kong, and the United States. Original illustration art from the best-known magazine illustrators is known to bring prices into the hundreds of thousands of US Dollars at auction. Norman Rockwell's work transcends even these high standards, with his painting "Breaking Home Ties" selling in a 2006 Sotheby's auction for USD15.4 million. The best-known pinup artists such as Gil Elvgren and Alberto Vargas also bring tremendous prices at auction, with a number of Elvgren's works having sold for over USD100,000 in Heritage Auctions.
Sports-related illustration from Punch Magazine circa 1910.
Digolo and Mazrui subcategorize illustration into the techniques, which are being applied, such as: drawing, painting, printing, and pasting. These techniques affect the art in various ways, being chosen for the different impact the chosen medium produces. The choice can be based on the requirements of the illustration, constraints of the artist, cost, or other factors.
Various illustration techniques have been available to the artist over the centuries. The invention of paper pushed its boundaries even further. Traditional illustration focuses on reproducible ways of creating illustration and can be classified into different types:
Pen-and-ink illustration has been around in various forms. The Chinese Sumi-E can be attributed to this technique, incorporating the use of paints and dyes. Navigational maps have been produced using this technique in the 14-15th century. The technique has not fallen out of disuse and is still popular with artists and illustrators, due to its simplicity of use, drying time, and visual impact. Modern artists use a brush, pen or quill to achieve the desired effects, samples see references.
Illustration Great Egret by John James Audubon.
A natural history of birds: Illustrated with two hundred and five copper plates, curiously engraven from the life. And exactly colour'd by the author Eleazar Albin.
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- Archaeological illustration
- Art gallery
- Book illustration
- Concept art
- Communication design
- Graphic design
- Image development
- Information graphics
- Medical illustrator
- National Museum of American Illustration
- Technical illustration
- Top-left lighting
- cf. the freely available international Database of Scientific Illustrators 1450-1950 with 20 search fields and currently nearly 7000 entries of illustrators in science, medicine & technology active prior to 1950
- The R. Atkinson Fox Society: What Was the Golden Age of Illustration?
- Ivan Viola and Meister E. Gröller (2005). "Smart Visibility in Visualization". In: Computational Aesthetics in Graphics, Visualization and Imaging. L. Neumann et al. (Ed.)
- Industriegrafik.com website, Last modified: June 15, 2002. Accessed february 15, 2009.
- Norman Rockwell's Rising Value Prices Out His Museum Zac Bissonnette, AOL Daily Finance, 2-22-10
- Heritage Auctions search page
- Digolo & O. Mazrui (2005): Art & Design Forms 1 and 2, Page 51.
- Matthew Adam McLean (2007). The Cosmographia of Sebastian Münster, describing the world in the Reformation, Page 164.
- Pen-and-ink illustration, Art of M. Neschetna website, Last modified: January 15, 2011. Accessed: May 20, 2011.