Light, optics, and color:
the Impressionist eye
A triple revolution in the artist’s gaze

by C. Régnier, France

“Impressionism can be regarded as the child of the century of Science,” wrote Academician René Huyghe in the catalogue for the Centenary of Impressionism exhibition held in the Grand Palais, Paris, in 1974. The Impressionists had arrived on the scene “officially” a century earlier, in 1874, in tandem with a remarkable expansion in scientific and medical disciplines: optics, ocular physiology, clinical ophthalmology, retinal microscopy, photography, and colorimetry. The Impressionists were alert to some of these developments, but they painted above all from instinct or, if we go by Jean Renoir’s memoir, Renoir, my father, using a more specific part of their anatomy. Their attitude to science was ambivalent: they were adamant about opposing its claim to dictate their art, whether by its laws or by the unassailable logic of reasoning based on observation of the real world. And yet, in their signature subject matters—the representation of nature and 19th century bourgeois society— the Impressionists espoused a form of pictorial realism not so distant from the new laws being uncovered in optics, colorimetry, and ocular physiology. This disconcerted an audience unused to confronting the complexities of optical analysis: optics informs us that shadows are blue, whereas common sense tells us they are gray. The Impressionists banished subjectivity from their gaze, and with it any romantic view of the world, incurring indirect reproach for doing so.

Medicographia. 2011;33:92-100 (see French abstract on page 100)

In 1863, the selection committee of the Salon, the official art exhibition mounted by the Paris Academy of Fine Arts, turned down Le déjeuner sur l’herbe (The luncheon on the grass) by Édouard Manet (1832-1883), along with 3 000 other works (out of 5 000 submissions). The protests of the refusés reached the ears of Napoleon III, who authorized a Salon des Refusés at the Palais de l’Industrie. This counter-Salon drew mockery from the public and most critics, but attracted more visitors than its official counterpart.1

In 1874, Claude Monet (1840-1926), Pierre-Auguste Renoir (1841-1919), Henri Rouart (1833-1912), Camille Pissarro (1830-1903), and others established the Anonymous Cooperative Society of Artists (Painters, Sculptors, Engravers, etc) to organize their own annual exhibition, with no selection committee or prizes. Alfred Sisley (1839- 1899), Edgar Degas (1834-1917), and Berthe Morisot (1841-1895) joined them a little later. Over the next eight years, their exhibitions attracted enlightened art lovers and critics, thanks to an approach that broke with the academic representations ofthe time: its mission was to capture fleeting impressions and moving colors rather than transcribe stable images. French painters had previously been held in check by an academic training that focused on the technicalities of line while downplaying issues of color, which was viewed simply as an accident of light. Yet color was central to scientific and philosophical debates during this period.1,2

The Impressionist eye? Detail from Claude Monet’s Impression,
Sunrise (1872) Oil on canvas. Musée Marmottan, Paris.

© Giraudon/Bridgeman Giraudon.

From the Salon des Refusés to the salon of the Impressionists and their friends

The Company held its first exhibition in the former studio of the photographer Nadar (1820-1910) from April 15 to May 15, 1874. Bringing together 29 artists, it comprised 165 photographs, drawings, engravings, watercolors, and canvases. Monet exhibited twelve works, Pissarro five, Renoir six, Degas ten, and Sisley five. Despite opposition from Degas, Paul Cézanne (1839-1906) was allowed to exhibit three. Degas invited his protégés, headed by Morisot and Rouart, while Monet brought Eugène Boudin (1824-1898) and Pissarro introduced Édouard Béliard (1832-1912).

However, to their chagrin, their “master” Jean-Baptiste Corot (1796-1875) declined his invitation. “He remains the greatest,” wrote Degas in 1883, “he anticipated everything.”Monet added, “There’s only one master, Corot.We’re nothing in comparison, nothing.” Manet stayed away too, preferring to compete in official salons, as did Johan Jongkind (1819-1891). The exhibition drew only 3500 visitors compared to the 400 000 for the Salon des Refusés. Just fifteen paintings were sold. But press coverage was considerable, with eleven articles appearing under some well-known bylines between April 16 and May 7.3 Critics wrestled with names for the new school of painting. On April 25, writing in the satirical daily Le Charivari about the painting Monet had simply called Impression, Louis Leroy rebaptized it Impression, Sunrise and proceeded to lay on the irony: “Since I was impressed, there had to be some impression in it.” On April 29, the conservative La Presse referred to “the disciples of Monsieur Manet, pioneers of the painting of the future, the most determined and official of the School of Impression’s representatives.” The moderate, republican Le Siècle was more specific: “Once they’ve captured the impression, they say their role is finished.… Anyone wishing to characterize and explain them in a word would have to coin the term impressionists. They are impressionists in that they do not transcribe a landscape, but the sensation produced by the landscape.” OnMay 1, L’Artiste proposed: “If this little group were to set themselves up as a school, it should be called ‘The School of the Eyes’.” On May 7, Paris-Journal’s Ernest Chesneau came up with “The Outdoor School.” As for the artists themselves, who preferred the name “Independents,” they turned Le Charivari’s put-down on its head and proudly proclaimed themselves “Impressionists.”4

Nadar’s studio, at 35, boulevard des Capucines, Paris, where
Impressionism was born. France’s most celebrated photographer
of his time had a sign with his name on the building made by the
Lumière brothers, which was lit up with gas at nightfall.

© Undisclosed source/All rights reserved.

At their third exhibition in April 1877, the eighteen exhibitors founded the arts journal L’Impressionniste. Although only four issues ever appeared, all in 1877, the title made the name official. Indeed, the third exhibition only brought together Impressionist painters who referred to themselves as such. Around ten of the original artists fromthe 1874 exhibition dropped out, no longer considering themselves part of the new movement. Impressionists shared a number of attitudes and working techniques:
_ As rebels against the Academy, determined to steep themselves in contemporary reality and represent what they saw in ways that their audience could directly enjoy without special training, they refused to paint historical, mythological, or sentimental subjects;
_ Their analysis of light led them to load their palettes with pure colors only and apply the law of complementary colors; black was banished;
_ Realizing that complementary colors mutually intensify their luminosity when adjacent, but extinguish one another to grayblack when mixed, they applied pure colors in little brushstrokes;
_ Shunning studios, they often painted outdoors to better capture the light;
_ They relegated human figures to the distance, concentrating on light and atmosphere; and
_ They replaced dark shadowing in faces and light-colored clothing with cold tints, such as greens and blues, that generated a play of colors independent of the object’s shape.

Claude Monet’s
Oil on canvas. Musée Marmottan, Paris.

© Giraudon/Bridgeman Giraudon.

Edmond de Goncourt (1822-1896) identified their main influence as Japanese. Félix Bracquemond (1833-1914), an exhibitor at the 1874 Salon, had begun copying the works of Hokusai (1760-1849) as early as 1856, anticipating the “Japanism” that was to captivate many other Impressionists.4,5 The Impressionists dazzled their early supporters with their work with light, the novelty of their gaze, and their juxtaposition of colors, all of which ran parallel—indeed interweaved— with some of the scientific developments of the time, specifically in optics, colorimetry, ocular physiology, and the anthropology of vision.

Katsushika Hokusai (1760-1849): Sarumaru Daiyû from the series
One Hundred Poems by One Hundred Poets, Explained by a Wet
Nurse. Nishike-e etching. Musée Guimet, Paris.

© RMN (Musée Guimet, Paris)/Harry Bréjat.

Photography: a revolution for painters

The discovery of photography (etymologically, drawing with light) transformed the artists’ world, relieving them of the obligation to represent reality in a plethora of detail. The deconstruction of movement over time in series of still photographs (chronophotography) by Eadweard Muybridge (1830-1904) and Étienne-Jules Marey (1830-1904) revealed what the eye was unable to analyze alone. “What the eye has no time to grasp,” wrote Marey, “the camera translates… in the minutest detail.”

Manet and Degas worked from photographs. Frédéric Bazille (1841-1870) used a daguerreotype to produce his Naked young man lying on the grass (1870). All were unfazed by the contempt of Charles Baudelaire (1821-1867), who in 1859 wrote:

If photography is allowed to supplement art in some of its functions, it will soon have supplanted or corrupted it altogether, thanks to the stupidity of the multitude which is its natural ally. It is time for it to return to its true duty, which is to be the servant of the sciences and arts—but the very humble servant, like printing or shorthand, which have neither created nor supplemented literature.6

By relaxing the traditional approach to composition, with its formal opposition between subject and background, some Impressionist paintings resemble snapshots that capture a moment of time in the moving light of a landscape (or in people’s daily lives). In the ways they framed their subject matter and played with focus and space, the Impressionists took over a number of techniques from photography, while also showing that photography was not the only technique able to capture a fleeting gaze.5 The artist’s eye was often compared to an imperfect camera that the brain corrected or amplified. The engineer-historian Auguste Laugel (1830-1914) wrote:

Imagine a camera with a misaligned objective, defective lens, and a plate sensitive only in scattered areas. The photographer would be ill-prepared for taking a good picture. Yet all these faults and more we find in the human eye.7

The development of photography was punctuated by successive improvements in optical technique, notably objectives, shutters, and lenses. It also grew in parallel with striking advances in the exploration of the eye, notably the development of the ophthalmoscope.

The ophthalmoscope, chromatoscope, and Parinaud’s scale

In 1850, Hermann von Helmholtz (1821-1894), a professor of physiology and pathology in Königsberg, told his father:

I’ve invented something that will be extraordinarily useful in ophthalmology,…a combination of lenses that illuminate the dark retina through the pupil without using blinding light, yet at the same time display the retina in all its detail.…The transparent parts of the eye act as a magnifying glass, enlarging the retina twenty-fold.

Eadweard James Muybridge (1830-1904): Flying Cockatoo.
From: Animal Locomotion, Plate 758 (1887).

© NMeM/Science & Society Picture Library.

Étienne-Jules Marey (1830-1904). The Running Liontamer.

© Cinémathèque Française, Paris. All rights reserved.

Helmholtz demonstrated his ophthalmoscope in 1851. Between 1856 and 1861, he produced his , establishing the relationship between optics and ophthalmology. Describing it as “our specialty’s bible,” Edmund Landolt (1846-1926) added: “It shares with the other bible the fate of being read too little and understood even less.”8

Helmholtz’s ophthalmoscope (original model of 1852), constructed
by the instrument maker Emil Sydow in Berlin, and owned
and used by German ophthalmologist Friedrich von Graefe.

William Holland Wilmer Ophthalmology Collection/National Museum of Health &
Medicine, Washington, DC. © NMHM. With kind permission.

Polish-born Xavier Galezowski (1832-1907) was responsible for developing retinal chromatoscopy. His doctoral thesis, submitted in 1865, was entitled Ophthalmoscopy of changes in the optic nerve and the cerebral diseases on which they depend.9 In 1868, he published Retinal chromatoscopy in ocular diagnostics preceded by a study on the physical and physiological laws of colors,10 containing six plates showing a 44-shade color scale, four character scales to measure visual acuity (blood, blue, red, yellow), and a scale to measure astigmatism. Galezowski based ocular diagnostics on the study of color vision. Galezowski’s student Henri Parinaud (1844- 1905) became a leading French ophthalmologist during the Impressionist era. With clinical interests spanning neurology and ophthalmology, Parinaud was close to the renowned neurologist Jean-Martin Charcot (1825-1893), joining him at the Salpêtrière Hospital. His eponymous scale analyzing visual acuity in tenths using reading tests performed 33 cm from the eyes transformed the diagnosis of short-and long-sightedness and astigmatism into a routine procedure.8

“How to use Galezowski’s ophthalmoscope” from Xavier Galezowski’s
Traité des Maladies des Yeux [Treatise on the Diseases
of the Eyes].

Paris, France: J. B. Baillière, 1875.

Painters of light and color

What set the Impressionist school apart was their visual realism and enthusiastic deconstruction of light. In rebellion against time-honored chiaroscuro, Manet painted light-onlight. The luncheon on the grass marked the arrival of “light painting.” Most Impressionists painted in the open air; it was Manet who introduced Pissarro to outdoor painting. With the notable exception of Degas, it became their studio.

By painting in daylight, the Impressionists captured the ways in which landscape changes according to the time of day, climate, and season. In the 1890s, Monet tracked this perpetual variation in his serial studies of haystacks, poplars, and cathedrals. Sisley adopted a similar approach: “I always begin a picture with the sky because it determines the representation of matter, objects, time of day, and sunlight.”11 In the summer of 1869, Renoir worked with Monet on the technique of fragmenting color in light, first in views of the waterside café La Grenouillère in Chatou, a western suburb of Paris, and then on the banks of the Seine at Argenteuil. They painted leaves light green, and dabbed them with yellow sunlight. Renoir added touches of violet shade. The effect was to recreate the colors of the light spectrum.11

Vision, artists’ eyes, and science

Issues of vision, optics, and the health of artists’ eyes abounded in late 19th century literature. Physiologists, clinicians, and enlightened amateurs made learned attempts to explain the origin of art in terms of experimental method and scientific analysis. In his Optics and the arts, Laugel set vision above the other senses: “The eye makes us masters of everything and gives us a kind of hold over the world. It is our unrivalled instrument of knowledge…transporting us across space to the remotest worlds and allowing us to imagine infinity.” Vision was the supreme sensory perception and its corollary in art was painting.7

Helmholtz initiated the incursion of physiology and optics into the critical theory of painting, thanks to his interest in every component of vision: its physics (the emission and propagation of light), physiology (neuronal transmission of sensation), and psychology (perception). With Scottish physicist James Clerk Maxwell (1831-1879), he defined the three attributes of color: hue (red, etc), saturation (intense vs dull), and lightness (light vs dark). With Ernst Wilhelm von Brücke (1819-1892), a pioneer in the physiology of sensation and a major influence on Sigmund Freud, he published studies on the scientific principles behind the fine arts, in particular on the relationship between optics and painting.

Helmholtz and von Brücke recognized that the laws of physics were inadequate for representing objects colored by natural light. They warned artists not to make the mistake of trying to represent objects as we see them. Instead they lauded the changing role of light in the beauty of a painting: “A little more poetry and a little less strong sunlight would be highly desirable in our modern landscapes.” Explaining that air reflects blue light better than red light, but that red light comes into its own as the day advances, they advised painters not to hesitate in using violet, purple, or lilac colors (as Impressionists were often criticized for using). Von Brücke and Helmholtz recognized that the use of these colors “does not go well with the other colors in the landscape and readily destroys their harmony.” They also considered the spectator retina ill-prepared to accept jarring juxtapositions of colors. They concluded their attempt to bring science and art closer together with a defense and celebration of artistic genius:

What should a work of art, in the most elevated sense of the term, aim at? It should capture and excite our attention, and awaken a wealth of associated ideas and feelings lying dormant within our souls.…Only this appears to account for the power of art to move the human soul, which so often exceeds that of reality.12

Edouard Manet
(1832-1883). Le Déjeuner sur l’Herbe [The Luncheon on the Grass] (1863).
Oil on canvas (2.080×2.645 m).
Musée d’Orsay, Paris.

© RMN (Musée d’Orsay)/Hervé Lewandowski.
The controversy caused by the painting resulted in its rejection from the official Paris Salon exhibition by the jury, and led to the creation of the Salon des Refusés (Exhibition of Rejects), in 1863, with the blessing of Emperor Napoleon III.

Theories and disputes over color vision

The second half of the 19th century saw a huge increase in contributions to the theory of color vision. Between 1875 and 1879, close on 30% of papers on the physiology of optics were devoted to color vision, over double the proportion in 1870.

For French artists, the most popular and best-studied theoretician of color was Michel Eugène Chevreul (1786-1889), a national institution whose funeral at the grand old age of 102 was celebrated with all the pomp that the Third Republic could muster. Trained as an organic chemist, Chevreul was appointed director of the dye works at the Gobelins Manufactory in 1824, where he remained for half a century. The staff there complained about being unable to achieve a satisfactory effect with certain dyes. Chevreul discovered that although these dyes were chemically unstable, the real difficulty arose when using certain colors next to each other. In 1839, he published The principles of harmony and contrast of colours13 showing that colors are defined by the color of the objects around them. For any color to exist, it has to refer to its complementary color, which the eye tends to summon up more or less automatically. When presented with two (or more) colors, the eye makes an “optical mix” and creates a new color. Chevreul’s laws helped colorists to eliminate unwanted contrast effects. Using Newton’s corpuscular theory of light, he also produced a complete catalogue of color complementarity in a circular chromatic diagram that measured the effects of mutual proximity.14

The dye laboratory of the Manufacture des Gobelins in Paris, the
still extant royal tapestry factory founded by Louis XIV in 1662.

© Sergio Gaudenti/Kipa/Corbis.

Georges Seurat (1859-1891).
Un Dimanche Après-Midi à l’Île de la Grande Jatte [Sunday Afternoon on the Island of La Grande Jatte] (1884-1886).
Oil on canvas (207.5×308 cm).

The Art Institute of Chicago, Ill, USA. © The Art Institute of Chicago/
Bridgeman Giraudon.

Chevreul considered light the retinal “impression” of deconstructed radiation reflected by external objects. Helmholtz, on the other hand, viewed color as a sensation produced via sensory organs, believing that it resided neither in the object nor in the light that it reflected, but in the subject’s visual apparatus. “Impressionists” and “sensationists” were locked in dispute.15

Eugène Delacroix (1798-1863) and the Impressionists knew about Chevreul. For example, rather than use green, they knew that applying blue next to yellow would induce the eye and brain to generate the color green. Georges Seurat (1859- 1891) put theory into practice by painting outdoor scenes using minute dots of pure color (Pointillism), placing greens next to reds in a way that the eye combines into yellow, for example. The Impressionists were also familiar with the contrast between warm and cold colors. In Waterloo Bridge (1903), painted from his room in the Savoy Hotel, Monet set blue and orange next to one another, much like Renoir in Two sisters (On the terrace) (1881), in which he sets four complementary colors side by side. In 1879, the American Ogden Nicholas Rood (1831-1902) published his color wheel and three-constant color theory (purity, luminosity, and hue) that influenced the Neo-Impressionists and Pointillists, such as Seurat. “If we had to synthesize the various science-based methods employed in modern art,” wrote Pissarro, “we could say that they are based on Chevreul’s theory of colors, Maxwell’s experiments, and the measurements by N.O. Roods.” Pissarro, along with Seurat and Signac, were termed “scientific Impressionists.” In 1888, in France, Charles Henry (1859-1926) followed Roods with his own version of a color wheel based on wavelengths and the effects on recipient psychology. He in- spired both Seurat and Paul Signac (1863-1935).14 Other artists rejected the idea that scientific theory influenced their work.Renoir told the art dealer Ambroise Vollard (1866-1939):

The truth is that in painting, as in the other arts, nothing you do, however small, can be encapsulated in a formula.…You think you know a lot when you’ve learned from the ‘scientists’ that it’s the contrast between yellow and blue that produces violet shade, but in fact, having learned that, you still know absolutely nothing. There’s something extra about painting that can’t be explained and that’s essential.”15

In 1909, American artist Albert Henry Munsell (1858-1918) published his color system, which organized colors by hue, luminosity, and saturation (chroma). It became the most successful attempt at establishing a numerical color classification standard, and was adopted worldwide.15

Auguste Renoir (1841-1919). Les Deux Soeurs (Sur la Terrasse)
[Two Sisters (On the Terrace)]. Oil on canvas(100.5×81 cm).

The Art Institute of Chicago, Ill, USA. © The Art Institute of Chicago/Corbis.

Impressionists’ ocular pathology

Painters’ ocular pathology became a hot topic in the late 19th century.16 In 1863, one of Helmholtz’s students, Richard Liebreich (1830-1917), published and illustrated one of the first atlases of retinal ophthalmoscopy. In 1870, he gave a lecture in London entitled, “Turner and Mulready: Visual defects in painting,” which was published to great effect.17 Visitors to London galleries and museums were reported as donning magnifying glasses and color filters to reproduce the visual defects suffered by Turner and Mulready. Degas, who himself had a form of color blindness and loss of visual acuity, confirmed Liebreich’s contention that any painter with a visual disorder was likely to reproduce its effects in his art. Detractors felt vindicated in their distaste for the Impressionists’ work. Playwright August Strindberg (1849-1912) described Sisley’s work as “colorless, anemic, in a word albino.”18 L’Évènement’s art critic took a similar view: “I believe in my heart and soul that Monsieur Manet’s disciples are afflicted by color blindness.” Paul Mantz (1821-1895) at Le Temps, a future director of the School of Fine Arts, wrote: “With the works of some members of the group you can’t help thinking that they may have a physical eye disorder, or abnormalities of vision that would delight doctors in ophthalmology.”4

The Impressionist eye closes… Edgar Degas (1834-1917),
growing blind, increasingly turned to sculpture. La Petite Danseuse
[The Little Dancer].

Bronze (height, 98 cm). Musée d’Orsay, Paris. © RMN (Musée d’Orsay)/René- Gabriel Ojéda.

Pissarro for his part chuckled: “We’re afflicted with the painters’ disease, color blindness, the disease of the painters who see everything in blue,”19 whereas poet Jules Laforgue (1860- 1887) actually praised what he sensed as a physiological explanation for the Impressionists’ achievements, their “uncommon sensibility of eye.” By ignoring the collections of pictures in museums amassed through the centuries and their art school training, the Impressionists forged a new eye for themselves, sensitive only to luminous vibration. It saw naturally, and painted what it saw. To the three great illusions— line, perspective, and studio lighting—by which earlier technicians of painting had lived, the Impressionists responded with “vibration, contrast of color, and open air.” For Laforgue, there was no doubt: “The Impressionist eye is, in short, the most advanced in human evolution, the one which until now has grasped and rendered the most complicated combinations of nuances known.”20 _

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