Divisionism, also called chromoluminarism, is the characteristic style in Neo-Impressionist painting defined by the separation of colors into individual dots or patches that interact optically..Homer, William I. ''Seurat and the Science of Painting.'' Cambridge, MA: The MIT Press, 1964. By requiring the viewer to combine the colors optically instead of physically mixing

pigments A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

, Divisionists believed that they were achieving the maximum

luminosity Luminosity is an absolute measure of radiated electromagnetic radiation, electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electroma ...

scientifically possible.

Georges Seurat Georges Pierre Seurat ( , ; ; 2 December 1859 – 29 March 1891) was a French post-Impressionist artist. He devised the painting techniques known as chromoluminarism and pointillism and used conté crayon for drawings on paper with a rough ...

founded the style around 1884 as chromoluminarism, drawing from his understanding of the scientific theories of

Michel Eugène Chevreul Michel Eugène Chevreul (; 31 August 1786 – 9 April 1889) was a French chemist whose work contributed to significant developments in science, medicine, and art. Chevreul's early work with animal fats revolutionized soap and candle manufacturing ...

Ogden Rood Ogden Nicholas Rood (3 February 1831 in Danbury, Connecticut – 12 November 1902 in Manhattan) was an American physicist best known for his work in color theory. Career At age 18, Rood became a student at Yale University, but after his sophomor ...

and

Charles Blanc Charles Blanc (17 November 1813, Castres (Tarn) – 17 January 1882, Paris) was a French art critic. Life and career He was the younger brother of the French socialist politician and historian Louis Blanc. After the February Revolution of 1848 ...

, among others. Divisionism developed along with another style,

Pointillism Pointillism (, ) is a technique of painting in which small, distinct dots of color are applied in patterns to form an image. Georges Seurat and Paul Signac developed the technique in 1886, branching from Impressionism. The term "Pointillism ...

, which is defined specifically by the use of dots of paint and does not necessarily focus on the separation of colors.Ratliff, Floyd. ''Paul Signac and Color in Neo-Impressionism.'' New York: Rockefeller UP, 1992. .

Theoretical foundations and development

Divisionism is the technique of painting separate dots or patches of different colors in close proximity that interact optically in the viewer's perception to generate more luminous colors. The paints are not actually mixed but viewed close together, so the separate colors of light reflected by the paints mixes in the eye and brain; the process is called additive mixing and is also used by computer monitors. This is different from mixing different paints together to produce a new color by subtractive mixing, which is also how

laser printers Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively charged cylinder called a "drum" to d ...

produce colors. Despite the theory, Seurat's paintings don't actually use true additive mixture, since the colors reflected by his paints as he used them don't actually mix in the eye. Instead, Seurat used highly contrasting colors in close proximity, but not close enough to mix additively; this effect is called simultaneous contrast, which creates a mild shimmering appearance and slightly increases the colors' apparent visual intensity.

Impressionism Impressionism was a 19th-century art movement characterized by visible brush strokes, open Composition (visual arts), composition, emphasis on accurate depiction of light in its changing qualities (often accentuating the effects of the passage ...

originated in

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

in the 1870s, and is characterized by the use of quick, short, broken brushstrokes to accurately capture the momentary effects of light and atmosphere in an outdoor scene. The Impressionists sought to create an "impression" of a momentary scene as perceived by the viewer, rather than a mechanically precise replication of the scene. Divisionism, also known as

, developed from Impressionism in the 1880s. The Divisionists used a technique of placing small, distinct dots of color next to one another on the canvas, rather than mixing the colors on the palette. This created a more vibrant and dynamic effect, but also required a higher level of skill and precision. Neo-Impressionism emerged in the late 19th century, used more precise and geometric shapes to build compositions and was strongly influenced by the scientific study of

color theory Color theory, or more specifically traditional color theory, is a historical body of knowledge describing the behavior of colors, namely in color mixing, color contrast effects, color harmony, color schemes and color symbolism. Modern color th ...

and optical color effects, to create a more harmonious and luminous painting. Scientists or artists whose theories of light or color had some impact on the development of Divisionism include Charles Henry,

David Pierre Giottino Humbert de Superville David Pierre Giottino Humbert de Superville (The Hague, 18 July 1770 – Leiden, 9 January 1849) was a Dutch artist and art scholar. He was a draughtsman, lithographer, etcher, and portrait painter, and also wrote treatises on art, including the ...

, David Sutter,

and

Hermann von Helmholtz Hermann Ludwig Ferdinand von Helmholtz (; ; 31 August 1821 – 8 September 1894; "von" since 1883) was a German physicist and physician who made significant contributions in several scientific fields, particularly hydrodynamic stability. The ...

Beginnings with Georges Seurat

Divisionism, along with the Neo-Impressionism movement as a whole, found its beginnings in Georges Seurat's masterpiece, ''

A Sunday Afternoon on the Island of La Grande Jatte ''A Sunday Afternoon on the Island of La Grande Jatte'' () was painted from 1884 to 1886 and is Georges Seurat's most famous work. A leading example of pointillist technique, executed on a large canvas, it is a founding work of the neo-impress ...

''. Seurat had received classical training at the

École des Beaux-Arts ; ) refers to a number of influential art schools in France. The term is associated with the Beaux-Arts architecture, Beaux-Arts style in architecture and city planning that thrived in France and other countries during the late nineteenth centu ...

, and, as such, his initial works reflected the

Barbizon Barbizon () is a commune (town) in the Seine-et-Marne department in north-central France. It is located near the Fontainebleau Forest. Demographics The inhabitants are called ''Barbizonais''. Art history The Barbizon school of painters is n ...

style. In 1883, Seurat and some of his colleagues began exploring ways to express as much light as possible on the canvas.Sutter, Jean. ''The Neo Impressionists.'' Greenwich, CT: New York Graphic Society, 1970. . By 1884, with the exhibition of his first major work, ''

Bathers at Asnières ''Bathers at Asnières'' () is an 1884 oil on canvas painting by French artist Georges Pierre Seurat, the first of his two masterpieces on the monumental scale. The canvas is of a suburban, placid Parisian riverside scene. Isolated figures, with ...

'', as well as croquetons of the island of Île de la Jatte, his style began taking form with an awareness of Impressionism, but it was not until he finished ''La Grande Jatte'' in 1886 that he established his theory of chromoluminarism. In fact, ''La Grande Jatte'' was not initially painted in the Divisionist style, but he reworked the painting in the winter of 1885–86, enhancing its optical properties in accordance with his interpretation of scientific theories of color and light.Smith, Paul. Seurat, Georges. Grove Art Online. Oxford Art Online
/ref>

Paul Signac and other artists

Color theory

Charles Blanc's ''Grammaire des arts du dessin'' introduced Seurat to the theories of color and vision that would inspire chromoluminarism. Blanc's work, drawing from the theories of Michel Eugène Chevreul and

Eugène Delacroix Ferdinand Victor Eugène Delacroix ( ; ; 26 April 1798 – 13 August 1863) was a French people, French Romanticism, Romantic artist who was regarded as the leader of the French Romantic school.Noon, Patrick, et al., ''Crossing the Channel: ...

, stated that optical mixing would produce more vibrant and pure colors than the traditional process of mixing pigments. Mixing pigments physically is a subtractive process with cyan, magenta and yellow being the

primary colors Primary colors are colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printin ...

. On the other hand, if colored light is mixed together, an additive mixture results, a process in which the primary colors are red, green and blue. In Divisionist color theory, artists interpreted the scientific literature through making light operate in one of the following contexts: ;Local color: As the dominant element of the painting, local color refers to the true color of subjects, e.g. green grass or blue sky. ;Direct sunlight: As appropriate, yellow-orange colors representing the sun's action would be interspersed with the natural colors to emulate the effect of direct sunlight. ;Shadow: If lighting is only indirect, various other colors, such as blues, reds and purples, can be used to simulate the darkness and shadows. ;Reflected light: An object that is adjacent to another in a painting could cast reflected colors onto it. ;Contrast: To take advantage of Chevreul's theory of simultaneous contrast, contrasting colors might be placed in close proximity. Seurat's theories intrigued many of his contemporaries, as other artists seeking a reaction against Impressionism joined the Neo-Impressionist movement.

Paul Signac Paul Victor Jules Signac ( , ; 11 November 1863 – 15 August 1935) was a French Neo-Impressionist painter who, with Georges Seurat, helped develop the artistic technique Pointillism. Biography Paul-Victor-Jules Signac was born in Paris on ...

, in particular, became one of the main proponents of divisionist theory, especially after Seurat's death in 1891. In fact, Signac's book, ''D’Eugène Delacroix au Néo-Impressionnisme'', published in 1899, coined the term Divisionism and became widely recognized as the manifesto of Neo-Impressionism.

Divisionism in France and Northern Europe

In addition to Signac, other

French artists French may refer to: * Something of, from, or related to France ** French language, which originated in France ** French people, a nation and ethnic group ** French cuisine, cooking traditions and practices Arts and media * The French (band), ...

, largely through associations in the

Société des Artistes Indépendants The Société des Artistes Indépendants (, ''Society of Independent Artists'') or Salon des Indépendants was formed in Paris on 29 July 1884. The association began with the organization of massive exhibitions in Paris, choosing the slogan "''sa ...

, adopted some Divisionist techniques, including Camille and

Lucien Pissarro Lucien Pissarro (20 February 1863 – 10 July 1944) was a French landscape painter, printmaker, wood engraver, designer, and printer of fine books. His landscape paintings employ techniques of Impressionism and Neo-Impressionism, but he also ...

, Albert Dubois-Pillet,

Charles Angrand Charles Angrand (; 19 April 1854 – 1 April 1926) was a French artist who gained renown for his Neo-Impressionist paintings and drawings. He was an important member of the Parisian avant-garde art scene in the late 1880s and early 1890s. Early ...

Maximilien Luce Maximilien Luce (; 13 March 1858 – 6 February 1941) was a French Neo-impressionist artist, known for his paintings, graphic art and his anarchist activism. Starting as a wood-engraver, he subsequently concentrated on painting, first as a ...

Henri-Edmond Cross Henri-Edmond Cross (; 20 May 1856 – 16 May 1910), born Henri-Edmond-Joseph Delacroix (), was a French painter and printmaker. He is most acclaimed as a master of Neo-Impressionism and he played an important role in shaping the second phase ...

and Hippolyte Petitjean. Additionally, through Paul Signac's advocacy of Divisionism, an influence can be seen in some of the works of

Vincent van Gogh Vincent Willem van Gogh (; 30 March 185329 July 1890) was a Dutch Post-Impressionist painter who is among the most famous and influential figures in the history of Western art. In just over a decade, he created approximately 2,100 artworks ...

Henri Matisse Henri Émile Benoît Matisse (; 31 December 1869 – 3 November 1954) was a French visual arts, visual artist, known for both his use of colour and his fluid and original draughtsmanship. He was a drawing, draughtsman, printmaking, printmaker, ...

Jean Metzinger Jean Dominique Antony Metzinger (; 24 June 1883 – 3 November 1956) was a major 20th-century French painter, theorist, writer, critic and poet, who along with Albert Gleizes wrote the first theoretical work on Cubism. His earliest works, from 1 ...

Robert Delaunay Robert Delaunay (; 12 April 1885 – 25 October 1941) was a French artist of the School of Paris movement; who, with his wife Sonia Delaunay and others, co-founded the Orphism (art), Orphism art movement, noted for its use of strong colours and g ...

and

Pablo Picasso Pablo Diego José Francisco de Paula Juan Nepomuceno María de los Remedios Cipriano de la Santísima Trinidad Ruiz y Picasso (25 October 1881 – 8 April 1973) was a Spanish painter, sculptor, printmaker, Ceramic art, ceramicist, and Scenic ...

.Rapetti Rodolphe Signac, Paul Grove Art Online. Oxford Art Online
/ref> In 1907 Metzinger and Delaunay were singled out by the critic

Louis Vauxcelles Louis Vauxcelles (; born Louis Meyer; 1 January 187021 July 1943) was a French art critic. He is credited with coining the terms ''Fauvism'' (1905) and ''Cubism'' (1908). He used several pseudonyms in various publications: Pinturrichio, Vasari, ...

as Divisionists who used large, mosaic-like 'cubes' to construct small but highly symbolic compositions. Both artists had developed a new sub-style that had great significance shortly thereafter within the context of their Cubist works.

Piet Mondrian Pieter Cornelis Mondriaan (; 7 March 1872 – 1 February 1944), known after 1911 as Piet Mondrian (, , ), was a Dutch Painting, painter and Theory of art, art theoretician who is regarded as one of the greatest artists of the 20th century. He w ...

Jan Sluijters Johannes Carolus Bernardus (Jan) Sluijters, or Sluyters (17 December 1881 in 's-Hertogenbosch – 8 May 1957 in Amsterdam) was a Dutch Painting, painter and co-founder of the Moderne Kunstkring. Sluijters (in English often spelled "Sluyters") was ...

and Leo Gestel, in the Netherlands, developed a similar mosaic-like Divisionist technique circa 1909. The

Futurists Futurists (also known as futurologists, prospectivists, foresight practitioners and horizon scanners) are people whose specialty or interest is futures studies or futurology or the attempt to systematically explore predictions and possibilities ...

later (1909–1916) would adapt the style, in part influenced by

Gino Severini Gino Severini (7 April 1883 – 26 February 1966) was an Italian Painting, painter and a leading member of the Futurism (art), Futurist movement. For much of his life he divided his time between Paris and Rome. He was associated with neo-classici ...

's Parisian experience (from 1907), into their dynamic paintings and sculpture.

Divisionism in Italy

The influence of Seurat and Signac on some Italian painters became evident in the First Triennale in 1891 in

Milan Milan ( , , ; ) is a city in northern Italy, regional capital of Lombardy, the largest city in Italy by urban area and the List of cities in Italy, second-most-populous city proper in Italy after Rome. The city proper has a population of nea ...

. Spearheaded by Grubicy de Dragon, and codified later by Gaetano Previati in his ''Principi scientifici del divisionismo'' of 1906, a number of painters mainly in Northern Italy experimented to various degrees with these techniques. Pellizza da Volpedo applied the technique to social (and political) subjects; in this he was joined by Morbelli and Longoni. Among Pellizza's Divisionist works were ''Speranze deluse'' (1894) and ''Il sole nascente'' (1904). It was, however, in the subject of landscapes that divisionism found strong advocates, including

Giovanni Segantini Giovanni Segantini (15 January 1858 – 28 September 1899) was an Italian painter known for his large pastoral landscapes of the Alps. He was one of the most famous artists in Europe in the late 19th century, and his paintings were collected by ...

, Gaetano Previati, Angelo Morbelli and Matteo Olivero. Further adherents in painting

genre Genre () is any style or form of communication in any mode (written, spoken, digital, artistic, etc.) with socially agreed-upon conventions developed over time. In popular usage, it normally describes a category of literature, music, or other fo ...

subjects were

Plinio Nomellini Plinio Nomellini (6 August 1866, Livorno – 8 August 1943, Florence) was an Italian painter in the Divisionist style. Biography He was born to Coriolano Nomellini, a customs official, and his wife Cesira née Menocci.

, Rubaldo Merello, Giuseppe Cominetti, Camillo Innocenti, Enrico Lionne and Arturo Noci. Divisionism was also in important influence in the work of

(''Souvenirs de Voyage'', 1911);

Giacomo Balla Giacomo Balla (18 July 1871 – 1 March 1958) was an Italian painter, art teacher and poet best known as a key proponent of Futurism. In his paintings, he depicted light, movement and speed. He was concerned with expressing movement in his works ...

(''Arc Lamp'', 1909); Carlo Carrà (''Leaving the scene'', 1910); and

Umberto Boccioni Umberto Boccioni (; ; 19 October 1882 – 17 August 1916) was an influential Italian painter and sculptor. He helped shape the revolutionary aesthetic of the Futurism movement as one of its principal figures. Despite his short life, his approach ...

(''The City Rises'', 1910).Derived from paragraph i
Associazione Pellizza da Volpedo
, which cites Enciclopedia dell'arte, Milano (Garzanti) 2002, and also see Voci del Divisionismo italiano in Bollettino Anisa, N. 12 Anno XIX, n. 1, May 2000.

Criticism and controversy

Divisionism quickly received both negative and positive attention from

art critic An art critic is a person who is specialized in analyzing, interpreting, and evaluating art. Their written critiques or reviews contribute to art criticism and they are published in newspapers, magazines, books, exhibition brochures, and catalogue ...

s, who generally either embraced or condemned the incorporation of scientific theories in the Neo-Impressionist techniques. For example,

Joris-Karl Huysmans Charles-Marie-Georges Huysmans (, ; 5 February 1848 – 12 May 1907) was a French novelist and art critic who published his works as Joris-Karl Huysmans (, variably abbreviated as J. K. or J.-K.). He is most famous for the novel (1884, pub ...

spoke negatively of Seurat's paintings, saying "Strip his figures of the colored fleas that cover them, underneath there is nothing, no thought, no soul, nothing".Rewald, John. ''Seurat: a biography.'' New York: H.N. Abrams, 1990. . Leaders of Impressionism, such as

Monet Oscar-Claude Monet (, ; ; 14 November 1840 – 5 December 1926) was a French painter and founder of Impressionism painting who is seen as a key precursor to modernism, especially in his attempts to paint nature as he perceived it. During his ...

and Renoir, refused to exhibit with Seurat, and even

Camille Pissarro Jacob Abraham Camille Pissarro ( ; ; 10 July 1830 – 13 November 1903) was a Danish-French Impressionist and Neo-Impressionist painter born on the island of St Thomas (now in the US Virgin Islands, but then in the Danish West Indies). ...

, who initially supported Divisionism, later spoke negatively of the technique. While most divisionists did not receive much critical approval, some critics were loyal to the movement, including notably

Félix Fénéon Félix Fénéon (; 22 June 1861 – 29 February 1944) was a French art critic, gallery director, writer and anarchist during the late 19th century and early 20th century. He coined the term '' Neo-Impressionism'' in 1886 to identify a group of ...

Arsène Alexandre Arsène Alexandre (16 August 1859 – 1 October 1937) was a French art critic. He was a contributor to ''L'Événement'', ''Le Paris'' and ''L'Éclair'' and in 1894 was one of the founders of the satirical journal ''Le Rire'', becoming its arti ...

and Antoine de la Rochefoucauld.

Scientific misconceptions

Although Divisionist artists strongly believed their style was founded in scientific principles, some people believe that there is evidence that Divisionists misinterpreted some basic elements of optical theory.Lee, Alan. "Seurat and Science." ''Art History'' 10 (June 1987): 203-24. For example, one of these misconceptions can be seen in the general belief that the Divisionist method of painting allowed for greater luminosity than previous techniques. Additive luminosity is only applicable in the case of colored light, not juxtaposed pigments; in reality, the luminosity of two pigments next to each other is just the average of their individual luminosities. Furthermore, it is not possible to create a color using optical mixture that could not also be created by physical mixture. Logical inconsistencies can also be found with the Divisionist exclusion of darker colors and their interpretation of simultaneous contrast.

Gallery

File:Georges Seurat, 1889-90, Le Chahut, Kröller-Müller Museum (detail).jpg,

, 1889–90, '' Le Chahut'', Kröller-Müller Museum (detail) File:Theo Van Rysselberghe portrait-of-irma-sethe-1894.jpg,

Théo van Rysselberghe Théophile "Théo" van Rysselberghe (23 November 1862 – 13 December 1926) was a Belgian Neo-impressionism, neo-impressionist Painting, painter, who played a pivotal role in the European art scene at the turn of the twentieth century. Bi ...

, 1894, '' Portrait of Irma Sèthe'' File:Henri Matisse, 1899, Still Life with Compote, Apples and Oranges, oil on canvas, 46.4 x 55.6 cm, The Cone Collection, Baltimore Museum of Art.jpg,

, 1899, ''Still Life with Compote, Apples and Oranges'',

Baltimore Museum of Art The Baltimore Museum of Art (BMA) in Baltimore, Maryland, is an art museum that was founded in 1914. The BMA's collection of 95,000 objects encompasses more than 1,000 works by Henri Matisse anchored by the Cone Collection of modern art, ...

File:Pablo Picasso, 1901, Old Woman (Woman with Gloves), oil on cardboard, 67 x 52.1 cm, Philadelphia Museum of Art.jpg,

, 1901, ''Old Woman (Woman with Gloves, Woman With Jewelry)'',

Philadelphia Museum of Art The Philadelphia Museum of Art (PMA) is an List of art museums#North America, art museum originally chartered in 1876 for the Centennial Exposition in Philadelphia. The main museum building was completed in 1928 on Fairmount, a hill located at ...

File:André Derain, 1905, Le séchage des voiles (The Drying Sails), oil on canvas, 82 x 101 cm, Pushkin Museum, Moscow. Exhibited at the 1905 Salon d'Automne.jpg,

André Derain André Derain (, ; 10 June 1880 – 8 September 1954) was a French artist, painter, sculptor and co-founder of Fauvism with Henri Matisse. In 2025, all of Derain’s work entered the public domain in the United States. Life and career Early ...

, 1905, ''Le séchage des voiles (The Drying Sails)'',

Pushkin Museum The Pushkin State Museum of Fine Arts (, abbreviated as , ''GMII'') is the largest museum of European art in Moscow. It is located in Volkhonka street, just opposite the Cathedral of Christ the Saviour. The International musical festival Sviatos ...

File:Jean Metzinger, c.1905, Baigneuses, Deux nus dans un jardin exotique, oil on canvas, 116 x 88.8 cm, Colección Carmen Thyssen-Bornemisza.jpg,

, c.1905, '' Baigneuses, Deux nus dans un jardin exotique (Two Nudes in an Exotic Landscape)'', Colección Carmen Thyssen-Bornemisza File:Robert Antoine Pinchon, 1905, La Seine à Rouen au crépuscule, oil on paperboard, 65 x 54 cm.jpg, Robert Antoine Pinchon, 1905, ''La Seine à Rouen au crépuscule'' File:Robert Delaunay, c.1906, Paysage au disque solaire, oil on canvas, 54 x 46 cm, Musée National d'Art Moderne.jpg,

, 1906, ''Paysage au disque'',

Musée National d'Art Moderne The Musée National d'Art Moderne (; "National Museum of Modern Art") is the national museum for modern art of France. It is located in the 4th arrondissement of Paris and is housed in the Centre Pompidou. In 2021 it ranked 10th in the list of ...

File:La fuite des nymphes.jpg,

, 1906, ''La fuite des nymphes'',

Musée d'Orsay The Musée d'Orsay ( , , ) () is a museum in Paris, France, on the Rive Gauche, Left Bank of the Seine. It is housed in the former Gare d'Orsay, a Beaux-Arts architecture, Beaux-Arts railway station built from 1898 to 1900. The museum holds mai ...

File:Dune III, by Piet Mondriaan.jpg,

, 1909, ''Dune III'',

Gemeentemuseum Den Haag The Kunstmuseum Den Haag is an art museum in The Hague in the Netherlands, founded in 1866 as the Museum voor Moderne Kunst. Later, until 1998, it was known as Haags Gemeentemuseum, and until the end of September 2019 as Gemeentemuseum Den Haag. I ...

File:Paul Signac, 1909, The Pine Tree at Saint Tropez, oil on canvas, 72 x 92 cm, Pushkin Museum, Moscow.jpg,

, 1909, ''The Pine Tree at Saint Tropez'',

File:Gino Severini, 1911, Souvenirs de Voyage, oil on canvas, 47 x 75 cm, private collection.jpg,

, 1911, ''Souvenirs de Voyage'' (''Memories of a Journey, Ricordi di viaggio''), private collection File:Hippolyte Petitjean - Pont neuf.jpg, Hippolyte Petitjean, c.1912, ''Le Pont Neuf'',

Metropolitan Museum of Art The Metropolitan Museum of Art, colloquially referred to as the Met, is an Encyclopedic museum, encyclopedic art museum in New York City. By floor area, it is the List of largest museums, third-largest museum in the world and the List of larg ...

References

External links

Agence photographique de la réunion des Musées nationaux
{{Metzinger Post-Impressionism Impressionism Divisionist painters Pointillism