Monday, November 5, 2018

Willful blindness: the myth of white marble statues

Modern technology has confirmed an unpopular truth that has been overlooked or ignored by art history for centuries. The figures of gods and heroes created by Greek and Roman artists were once painted in brilliant colors. Marble was considered a canvas, not the finished product.

The myth of whiteness in classical sculpture began with the rediscovery of Greco-Roman sculpture during the early Italian Renaissance. While the durability of marble allowed the sculptures to survive the centuries, the paint did not survive. Buried objects retained more color, but traces of paint were often brushed or washed off during cleaning. The statues were understood to be from classical antiquity and were regarded as ideal models of artistic achievement. They had a profound influence, not only on Renaissance artists, such as Donatello and Michelangelo, but also on all art that followed. The misinterpretation of ancient sculpture began with an honest mistake, but as new evidence was found to suggest the sculptures were painted, the myth persisted.

When the ancient Roman cities of Pompeii and Herculaneum were excavated in the mid-eighteenth century, the noted art historian Johann Winckelmann saw some of the artifacts and noticed the remnants of color, but chose to ignore the evidence. Instead, he attributed a statue of Artemis, with red hair, red sandals, and a red quiver strap, as Etruscan rather than Greek. He declared, “The whiter the body is, the more beautiful it is.” In Germany, Goethe declared that “savage nations, uneducated people, and children have a great predilection for vivid colors.”

Major excavations in the nineteenth century exposed more painted reliefs and sculptures, but scholars who tried to discuss polychromy (the art of painting sculpture) were dismissed. The great sculptor Auguste Rodin supposedly said, while pounding his chest, “I feel it here that they were never colored.”

Willful blindness had taken hold and the myth persisted.

Art restorers, art dealers, and even museums felt it necessary to scrub and polish Greek and Roman objects to a pristine whiteness. The core identity of Western civilization was built on a story of Greek superiority, and that included the perception of white marble statuary as a standard of beauty. Recently, however, modern technology and technical innovation have reaffirmed what is, without a doubt, the truth: the classical ideal of white marble statues is based on a lie. Greek and Roman statues were painted.

In the 1980’s, Vinzenz Brinkmann, while pursuing a degree in classics and archaeology in Munich, used a special lamp to highlight the surface relief on statuary. While finding little evidence of tool marks, he did find significant evidence of polychromy. He soon realized, however, that this discovery did not necessarily require a special lamp. He recalled some of the pigment “was easy to see, even with the naked eye. It turns out vision is highly subjective.”

Mark Abbe was a graduate student working in the ancient city of Aphrodisias (in present-day Turkey) in 2000, when he first saw statues with flecks of color: red pigment on lips, black on hair, and gilding on limbs.  “The visual appearance of these things was just totally different from what I’d seen in the standard textbooks . . .” Now a professor of ancient art and a leading scholar of Greek and Roman polychromy, Abbe says the idea the ancients disliked color “is the most common misconception about Western aesthetics in the history of Western art.”

In recent years it’s become easier to detect pigments from the fragments of paint that remain. Brinkmann and his wife, Ulrike Koch-Brinkmann, began recreating Greek and Roman sculpture with an approximation of their original colors. “Gods in Color”, an exhibition of these replicas, began in 2003 and toured twenty-eight cities. Some scholars, however, while supportive of the work, have noted the reconstructions are too opaque and flat. Plaster, which the replicas were made of, absorbs paint, while marble does not. They have also noted the lack of nuance and individual style which they presume would have been evident in the originals. 

There is optimism that more information and other types of reproductions, such as digital reproductions, will permit a more nuanced and naturalistic interpretation of how these ancient statues once looked. Museum curators are beginning to reevaluate their exhibits. Enhanced displays, better museum signage, and computerized light projections will help to correct the misinformation about Greek and Roman sculpture.

Only time will tell, however, if the myth is more powerful than the truth.

The Myth of Whiteness in Classical Sculpture by Margaret Talbot, The New Yorker

Wednesday, August 22, 2018

The revision of vision

I have persistently written about the limitations of vision and how language can affect our perceptions. In “Why naming the ‘thing’ can be a problem” I pointed out how language defines our visual interpretations. Another post, “Intuition is just another form of pattern recognition”, was also about the limitations of language description and the importance of trying to find new patterns by defining information in a different way.

When I posted “Shades of Truth” at the beginning of August this year, I was reminded, yet again, of the similarities to an essay I came across in the Disney Imagineering Library in Glendale, CA many years ago.  The essay was “The Revision of Vision”  by S.I. Hayakawa (1906-1992), a linguist, psychologist, and teacher. It was written as an introduction to the book "Language of Vision" by Gyorgy Kepes. There are many writings that have impacted my interpretations of painting and art, and this essay is certainly at the top of my list.

The Revision of Vision

by S.I. Hayakawa, Illinois Institute of Technology 

Introductory essay for "Language of Vision" by Gyorgy Kepes, originally published in 1944

Whatever may be the language one happens to inherit, it is at once a tool and a trap. It is a tool because with it we order our experience, matching the data abstracted from the flux about us with linguistic units: words, phrases, sentences. What is true of verbal languages is also true of visual "languages": we match the data from the flux of visual experience with image-clichés, with stereotypes of one kind or another, according to the way we have been taught to see.

And having matched the data of experience with our abstractions, visual or verbal, we manipulate those abstractions, with or without further reference to the data, and make systems with them. Those systems of abstractions, artifacts of the mind, when verbal, we call "explanations," or "philosophies"; when visual, we call them our "picture of the world."

With these little systems in our heads we look upon the dynamism of the events around us, and we find, or persuade ourselves that we find, correspondences between the pictures inside our heads and the world without. Believing those correspondences to be real, we feel at home in what we regard as a "known" world.

languages select . . . they leave out what they do not select.

In saying why our abstractions, verbal or visual, are a tool, I have already intimated why they are also a trap. If the abstractions, the words, the phrases, the sentences, the visual clichés, the interpretative stereotypes, that we have inherited from our cultural environment are adequate to their task, no problem is presented. But like other instruments, languages select, and in selecting what they select, they leave out what they do not select. The thermometer, which speaks one kind of limited language, knows nothing of weight. If only temperature matters and weight does not, what the thermometer "says" is adequate. But if weight, or color, or odor, or factors other than temperature matter, then those factors that the thermometer cannot speak about are the teeth of the trap. Every language, like the language of the thermometer, leaves work undone for other languages to do.

Visually, the majority of us are still "object-minded" and not "relation-minded". 

. . . Revisions of language are needed. Every day we are, all of us, as persons, as groups, as societies, caught in the teeth of what the older languages leave completely out of account. We talk of a new, shrunken, interdependent world in the primitive smoke-signals of "nationality," "race" and "sovereignty". We talk of the problems of an age of international cartels and patent monopolies in the economic baby-talk of Poor Richard's Almanack. We attempt to visualize the eventfulness of a universe that is an electro-dynamic plenum in the representational clichés evolved at a time when statically-conceived, isolable "objects" were regarded as occupying positions in an empty and absolute "space". Visually, the majority of us are still "object-minded" and not "relation-minded". We are the prisoners of ancient orientations imbedded in the languages we have inherited.

The language of vision determines, perhaps even more subtly and thoroughly than verbal language, the structure of consciousness. To see in limited modes of vision is not to see at all - to be bounded by the narrowest parochialisms of feeling.

. . . Purposely depriving us of the easy comfort of all aesthetic stereotypes and interpretative clichés, Mr. Kepes would have us experience vision as vision. (His) endeavor may perhaps best be characterized by the following analogy. To a Chinese scholar, the pleasure to be derived from an inscription is only partly due to the sentiments it may express. He may take delight in the calligraphy even when the inscription is meaningless to him as text. Suppose now a singularly obtuse Chinese scholar existed who was solely preoccupied with the literary or moral content of inscriptions, and totally blind to their calligraphy, How would one ever get him to see the calligraphic qualities of an inscription, if he persisted, every time the inscription was brought up for examination, in discussing its literary content, it accuracy or inaccuracy as statement of fact, his approval or disapproval of its moral injunctions?

Something of the quality of a child's delight in playing with colors and shapes has to be restored to us before we learn to see again . . .

It is just such a problem that faces the contemporary artist, confronted with a public to whom the literary, sentimental, moral, etc., content of art is art - to whom visual experience as such is an almost completely ignored dimension. . . . We have all been taught, in looking at pictures, to look for too much. Something of the quality of a child's delight in playing with colors and shapes has to be restored to us before we learn to see again, before we unlearn the terms in which we ordinarily see.

...How we deal with reality is determined at the moment of impact by the way in which we grasp it. Vision shares with speech the distinction of being the most important of the means by which we apprehend reality.

When we structuralize the primary impacts of experience differently,we shall structuralize the world differently.

To cease looking at things atomistically in visual experience and to see relatedness means, among other things, to lose in our social experience... the deluded self-importance of absolute "individualism" in favor of social relatedness and interdependence. When we structuralize the primary impacts of experience differently, we shall structuralize the world differently.

The reorganization of our visual habits so that we perceive not  isolated "things" in "space" but structure, order, and the relatedness of events in space-time, is perhaps the most profound kind of revolution possible - a revolution that is long overdue not only in art, but in all our experience.

Wednesday, August 1, 2018

Shades of truth

A while back I posted an article titled “Do facts matter or is truth just another possibility?”. I wrote about our outdated, misleading primary color system and the confusion it can cause. I also mentioned the inaccuracies of the most commonly used world map (Mercator) and how its distortions affect our perceptions. In a follow-up article “A win for visual truth” I covered a new design for a world map, called the Authagraph Map – it looks strange, but is far more accurate than the Mercator map. I don’t know that we will soon be using a more accurate color primary system, or a more accurate world map, but I do hope that we can learn new information and resist the temptation to treat our version of reality as some kind of worn-out shoe that we keep around just because it’s comfortable.

Now along comes an article from – another great example of misleading perceptions, how more information is better information, and how nuance can be as important or even more important than simplicity.

Is the US Leaning Red or Blue? It All Depends on Your Map

by Issie Lapowsky,
For the complete article click here.

On May 11, 2017, a reporter named Trey Yingst, who covers the White House for the conservative news network OANN, tweeted a photo of a framed map of the United States being carried into the West Wing. The map depicted the 2016 election results county-by-county, as a blanket of red, marked with flecks of blue and peachy pink along the West Coast and a thin snake of blue extending from the northeast to Louisiana. It was a portrait of the country on election night, but on Twitter, it was also a Rorschach test.

Conservatives replying to Yingst's tweet interpreted the expanse of red as proof of their party's dominance throughout all levels of government. Liberals viewed the map as a distortion, masking the fact that most of that redness covers sparsely populated land, with relatively few voters.

In reality, both sides are right, says Ken Field. A self-proclaimed "cartonerd," Field is a product engineer at the mapping software company Esri and author of a guidebook for mapmakers called Cartography. The problem, he says, isn't with people's partisan interpretation of the map. The problem is believing that any single map can ever tell the whole story. "People see maps of any type, and particularly election maps, as the result, the outcome, but there are so many different types of maps available that can portray results in shades of the truth," Field says. "It’s a question of the level of detail that people are interested in understanding."

It stands to reason that President Trump would want that particular map hung in the West Wing. There is an awful lot of red on it. But focusing on that map alone could lead Republicans to overestimate their advantage, and lead Democrats to misunderstand the best ways to catch up. That's one reason why Field recently published an extensive gallery of more than 30 alternative maps designed to tell markedly different stories about what happened on election night 2016. 

"All of these maps show different versions of the truth," he says. "None are right, and none are wrong, but they all allow you to interpret the results differently."

Take the map Yingst shared, for example. In the language of mapmakers, it’s a “choropleth diverging hue map.” The term “choropleth” refers to maps that use color or shading to visualize a given measurement. In this case, the map uses either the color red or blue to indicate which party won a given county. It’s accurate, and it’s familiar. These colored county-level or state-level maps are some of the most commonly used to illustrate the results of an election. But, Field says, they also lack nuance. There’s nothing on that map to indicate to the viewer, for instance, that fewer votes were cast in the rural mountainous regions of Montana than in Manhattan.

Understanding that nuance—or lack thereof—is key heading into the 2018 midterms, when amateur cartographers will no doubt climb out of Twitter’s recesses to proclaim their definitive readings of electoral maps. Here’s what we can learn from just a few of Field’s examples:

The Pointillism Approach

Presidential election 2016: dasymetric dot density KEN FIELD

To Field, there's no such thing as a totally comprehensive map, but he says, "Some are more truthful than others." The so-called dasymetric dot density map is one of them. The term “dasymetric” refers to a map that accounts for population density in a given area. Instead of filling an entire state or county with the color red or blue to indicate which party won, Field uses red and blue dots to represent every vote that was cast. On this particular map from 2016, there are roughly 135 million dots. Then, rather than distributing the dots evenly around a county, he distributes them proportionally according to where people actually live, based on the US government's National Land Cover Database. That’s to avoid placing lots of dots in, say, the middle of a forest, and to account for dense population in cities.

Taken together, Field says, these methods offer a far more detailed illustration of voter turnout than, say, the map in Yingst’s tweet. That map uses different shades of red and blue to indicate whether candidates won by a wide or slim margin. But by completely coloring in all the counties, it gives counties where only a few hundred votes were cast the same visual weight as counties where hundreds of thousands of votes were cast. So, the map looks red. But on the dasymetric dot density map, it’s the blue that stands out, conveying the difference between the popular vote, which Clinton won, and the electoral college vote, which Trump won.

Shades of Red and Blue

Presidential election 2016: Value-by-alpha KEN FIELD

The value-by-alpha map is similar to the dasymetric dot density map, and in some ways, even simpler. It doesn’t account for where votes were most likely cast within a county. Instead, it uses color to indicate the party’s vote share in each county, and opacity (in mapmaking, it’s called the “alpha channel,” hence, value-by-alpha) to indicate the population in a given area of the county. A bright, vibrant blue indicates a high Democratic vote share in a densely populated area. A light pink indicates a high Republican vote share in a sparsely populated area. Purples portray areas where one party or another won by a narrow margin.

What you notice first when you look at the map is that the solid red wall extending from North Dakota to Texas on the map Yingst shared is almost white in this rendering. What you notice second is just how much purple there is everywhere else. It’s a good reminder of what people often forget about the 2016 election: “It was very close,” Field says. President Trump won Michigan, Wisconsin, and Pennsylvania, the three states that clinched his victory, by about one percentage point or less.

The View from Above

See link to article above for the complete interactive map.
What Field likes most about the 3D prism map is how people react to it. “It’s just cool. People like 3D stuff,” he says. But it also illustrates an important point. Counties are colored red or blue, based on which party won, but the vote totals are portrayed in three dimensions, where the height is equal to the number of votes cast for the winning party. Because Clinton predominantly won big cities, where more votes are cast, it creates a map that looks a bit like a city itself, with dozens of mile-high blue skyscrapers jutting out from between red row-homes and strip malls.

Click around the map and you’ll see that viewed from above, it looks not unlike Trump's map—all in red. But click to tilt the map and it’s mostly blue spikes. It demonstrates perhaps more effectively than any of the other maps how President Trump won in 2016, Field says. “You had a Republican who was very successful in getting the smaller areas to vote Republican, while the larger populated major cities went Democrat,” he says.

Wednesday, May 2, 2018

Simplicity, complexity, and snowflakes

Nikolai Timkov "A Bright Day" 1963

Next winter, if you are fortunate enough to enjoy a bright, sunlit, snow-covered landscape, remember you are looking at all the colors of the rainbow. When sunlight hits snow, its full spectrum of wavelengths is almost entirely reflected back at us – every spectral color – red, orange, yellow, green, blue, and violet.

Notes for painters:
  • Simplicity and complexity coexist, just as light and shadow, and warmer and cooler colors coexist. This is all part of the variety in unity. A memorable painting is one in which all the pieces combine to form something new, one in which the whole is greater than the sum of its parts.
  • Complexity does not necessarily mean more detail. Texture, color pattern, and variety in shapes and edges all contribute to the perception of complexity.
  • Learning to see complexity is a form of understanding; editing the information one sees is the key to a strong and insightful painting.

“Science is nothing other than the search to discover unity in the wild variety of nature, or more exactly, in the variety of our experience. Poetry, painting, the arts are the same search for unity in variety.” J. Bronowski (1908-1974) was a British mathematician, historian of science, theatre author, poet and inventor. He was also the presenter and writer of the 1973 BBC television documentary series and accompanying book The Ascent of Man.

“The measure of aesthetic value is in direct proportion to order and in inverse proportion to complexity.” George David Birkhoff (1884-1944) was another prominent mathematician who proposed a theory of measuring beauty in the book Aesthetic Measure.  

Birkhoff defined a typical aesthetic experience as a combination of three successive phases: (1) the act of attention, that increases proportionally to the observed object’s complexity (C); (2) the feeling of value or aesthetic measure (M); and (3) the realization that the object is characterized by a certain harmony or order (0). The mathematical formula he proposed defined the relationship of the three phases.

While the proposal of a formula to measure aesthetics may be interesting to some, most of us would probably just experience an eye-crossing moment of “huh?” But the take-away on this is the recognition of the relationship of simplicity and complexity, or as Bronowski pointed out – the unity in variety. Complexity is responsible for increasing the observer’s attention. Simplicity and the perception of order and pattern trigger a sense of answer or completion – a brief aha moment of “yes, this makes sense”. This is merely recognition of orderliness in a universe that is also dynamic and continually changing. 

Fedor Zakharov
Order and change, unity and variety, and simplicity and complexity are complementary. They co-exist in a continual feedback and response loop. How these elements coexist, and in what kind of proportional relationship, determine how a painting, or any other object we choose to create, looks and feels.

The visual aesthetics of snowflakes

Simplicity and complexity were the focus of researchers at Western Kentucky University who set out to quantify aesthetic experience by asking subjects to rate the perceived beauty of snowflakes and solid objects. Participants were presented with a set of ten snowflake silhouettes created from photographs of natural snowflakes that varied in complexity and ten randomly-shaped, computer-generated, solid objects that also varied in complexity. The results for the solid objects showed a preference for both the most and least complex objects, while moderately complex objects were rarely selected. The results for the snowflakes, however, were different. The least complex snowflakes were almost never chosen: 91 percent of participants perceived only the complex snowflakes as the most beautiful. 

The infinite variety of snowflakes

We have a tendency to overlook complexity when categorizing and visualizing information. The iconic image of a paper cut-out snowflake is probably the first visual that comes to mind when one mentions the word “snowflake”, but it’s suggested from the WKU study that people respond positively to complexity in natural forms when given a choice. It is also possible people are responding to complexity in conjunction with, not apart from, a sense of perceived order.

Chaos and order are defining features of the natural world. While the basic structure of a snowflake is determined by the scientific process of crystallization and all snowflakes start out in the same way, the actual formation of a snowflake is dependent on more chaotic atmospheric conditions, such as temperature and humidity. A snowflake’s growth is one of both order and chaos. No two falling snowflakes will meet precisely the same circumstances on their way to the ground; even the appearance of symmetry will be an illusion since the microscopic space of the growing crystal will contain subtle differences.

The process of snowflake formation is a perfect example of simplicity and complexity. It is also a perfect example of the dynamic forces of chaos and symmetry that create form in both nature and art.

Photo of natural snowflakes by Kenneth G. Libbrecht

Sunday, March 4, 2018

Breaking the "rules" and changing the parameters of perception

“When the great English painter Sir Joshua Reynolds explained to his students in the Royal Academy that blue should not be put into the foreground of paintings but should be reserved for the distant backgrounds . . . his rival Gainsborough – so the story goes – wanted to prove that such academic rules are usually nonsense. He painted the famous ‘Blue Boy’, whose blue costume, in the central foreground of the picture, stands out triumphantly against the warm brown of the background.”
(E. Gombrich, The Story of Art)

The complexity and endless variety of color information should make any painter wary of rules that limit possibilities. The history of art reveals a pattern of experimentation, innovation, and visual interpretation that form a fascinating time-line of both continuity and change.

We can see millions of colors, far more than we are able to mix with pigments. Also, the range of value (luminance) in a natural scene is almost always far larger than the range of values one can achieve with pigments. According to Margaret Livingstone (Vision and Art), the range of luminance in a room lit by a window or lamp may vary by hundreds of times, and the luminance in an outdoor scene can vary by a factor of a thousand. The range of values available using paint or photographic paper varies, at most, by a factor of twenty.

Artists have dealt with these limitations for centuries. There is not one solution for interpreting a three-dimensional scene on a two-dimensional surface using pigments which can never equal the contrast range or the colors we actually see.  But great artists throughout various periods of art history made one discovery after another that allowed them to interpret and create a convincing picture of the visible world.

The use of oil paint in the fifteenth century led to a greater range of rich colors and smooth gradations of tone.  There was the discovery of linear perspective, atmospheric perspective, and the use of strong tonal contrast known as chiaroscuro. Over the centuries artists refined these techniques and learned to optimize their command of value pattern and luminance to represent depth on a two-dimensional surface.

Value (luminance) determines our perception of depth, three-dimensionality, movement, and spatial organization. Perceiving light is simpler than discriminating what wavelength (color) it is.

Towards the end of the nineteenth century, there was a break with tradition when artists rebelled against the teachings of the academies and what they saw as predictable and uninspired painting. They realized traditional art, with its emphasis on defining objects with careful shading, did not reflect the reality of the scene outside the window. There are harsh contrasts in sunlight, shadows are not uniformly grey, black or brown, and reflections of light and the kind of light affect our perception of color.

These artists, known as Impressionists, set out on a path of discovery - the exploration of light and color. Empowered by the invention of the tin paint tube, they took painting outdoors to create unplanned and spontaneous paintings. Even those who remained studio painters, such as Edgar Degas, shared an interest in scenes that appeared unplanned and spontaneous, as if capturing a split-second glimpse of the world. The advent of photography and exposure to Japanese prints expanded the acceptance of compositions which were once considered unbalanced and incomplete.

The Impressionists, in a radical departure from Renaissance ideals, emphasized light and color, and the transitory nature of visual reality, instead of value and rounded, modeled, solid form. Their use of color changed painting in new and challenging ways, and the change was dramatic. What mattered in painting was not the subject, but the way in which it was translated into color. The old rules of predictable compositions, correct drawing and idealized or picturesque subject matter were set aside for new freedoms of expression in painting. But while the Impressionists were painting a new chapter in art history, some artists found the brushwork and flickering color too messy and incomplete. 

Mont Sainte Victoire by Paul Cezanne, 1895
Cezanne worked to bring solidity, order and design to the Impressionist’s use of light and color without resorting to the academic conventions of drawing and shading.

The Post-Impressionists, such as Cezanne, Seurat, Gauguin, and Van Gogh, brought a desire for order and solid form to the fleeting observations of the Impressionists, but did not want to return to the traditional methods for defining space and modeling form. These artists, while distinctively different from one another, worked to reconcile the pattern and solidity of visual reality with the brilliance and luminosity of color.

The Sower by Vincent Van Gogh, 1888
Van Gogh didn’t hesitate to distort and exaggerate information while using bright color and expressive brushwork.

 Self Portrait by Paul Gauguin, 1890-91
Images that looked flat did not bother Gauguin who sacrificed spatial depth in favor of pattern and color.
The pattern of innovation and change continued as each artist explored various facets of representation. Their work inspired other artists who moved in even different directions. The pointillism of George Seurat inspired Paul Signac’s paintings. Signac’s use of pure color in complementary pairs inspired Henri Matisse. Matisse and fellow painter Andre Derain continued the use of complementary color, but substituted painterly brushwork for the dots used by Signac and Seurat,  All of these painters expanded the dialogue of visual language and changed our ideas about visual interpretation.

The Pine Tree at Saint Tropez by Paul Signac, 1909

Montagne a Collioure by Andre Derain
Woman with the Hat by Henri Matisse,1905
This is an extreme example of Matisse' work during the Fauve period.  He discovered he could use any color as long as the value was accurate. Note the lack of any coherent color pattern. The warmer and cooler colors jump around at random with no reference to the actual light source. The darkest value in the painting is the anchor that holds everything together. Matisse's Self-Portrait-1906 still maintains strong color and brushwork, but has a more coherent, although unusual, color pattern.

Self Portrait by Henri Matisse 1906

Complementary colors are pairs of colors which, when combined, cancel each other out. When placed next to each other, they create strong and brilliant contrast. In the traditional red-yellow-blue color model, the complementary color pairs are red–green, yellow–purple, and blue–orange. The modern color model is cyan-magenta-yellow, and the complementary pairs are red-cyan, blue-yellow, and green-magenta.

Color is a property of light and light is not a random scattering of color. Wavelengths of light that we can see range from the longest (red) to the shortest (violet). The pattern of visible light is red, orange, yellow, green, blue, and violet. The colors merge seamlessly from one to the other. We see these colors because of the receptors in our eyes that are responsive to this narrow range of wavelengths. Objects absorb or reflect particular wavelengths of the visible spectrum. What we see are the wavelengths that are reflected back. 

We rarely perceive pure colors, and the colors we do see depend on the available light source. When the light changes, the number and ratio of wavelengths also change.