Thursday, January 31, 2008


The taboret is a little drawer unit that sits to the right of me me when I’m painting in oil in the studio. It holds paints, brushes, pens and pencils.

The white palette surface where I mix my paints rests on a hinged board which can can be set to any angle. If I need to refer to the color wheel (see posts on color), I can hook it above the mixing surface.

1. The blobs of paint squeezed from the tube rest on a 3x18 inch paint shelf. This is a wooden plywood surface that floats above the mixing surface.
2. I mix paints with a palette knife on a roll of standard white freezer paper, which is coated with polyethylene. The roll hangs on a wooden dowel below the paint shelf (see photo below).
3. Mixing cups with Grumtine and Liquin. Little wedges nearby hold the paper in tightly.
4. Peanut butter jar with kerosene for cleaning brushes. There’s a screen halfway down inside the jar to give something for the brush to scrub against.
5. Jar of Liquin, an alkyd based medium. It dries fast, but with a dull sheen that needs to be varnished later.
6. Plastic tub from a Chinese restaurant. I cut a rectangular hole in the lid with a mat knife. At the end of the day I scrape down the paints on the paint shelf using a palette knife, and the scrapings go in here. When it’s full, I dispose of the whole tub.
7. Paint rag with a wiggly wire to hold the brush handles. This is where brushes sit while they’re in use.
8. Note the door hinges under the mixing panel. This allows the whole panel to be raised up. Unseen beneath the hinged panel, is an adjustable sliding clamp that fixes the slope at any angle.
9. Brushes are mostly bristles and white nylon flats.

Here’s how the freezer paper fits under the edge of the tip-up palette. Fresh paper unrolls with the plastic side up, and constantly gives a new surface for mixing. The used paper tears off on the right of the palette.

In drawers below are pencils, pens, markers, paints, and mediums.

The whole thing is on wheels, allowing it to roll around.

Tomorrow: Downfacing Planes

Wednesday, January 30, 2008

Dinotopia in DeathRay

Readers of Dinotopia: Journey to Chandara will want to check out the six page feature in the new issue of DeathRay magazine, now on newsstands in the U.S.A and the UK. There’s also an interview with Spiderwick creator and artist Tony DiTerlizzi.

Line and Wash

Here’s a sketch from Jerusalem. It’s an example of the “line and wash” technique, a favorite with travel sketchers.

The line is pencil, and the wash is ivory black watercolor mixed with water in a film can, whose snap-on lid never leaks. It’s one of the easiest ways to get started with painting on the spot, because the tools are so simple. It all fits in your pocket.

May I show you a page from my wife Jeanette’s sketchbook? The line is from a ballpoint pen, and the washes are raw sienna, ultramarine, and burnt umber watercolors. She was thinking of the colors that John Singer Sargent used in his Venetian watercolors (too bad it's Poughkeepsie, not Venice). To see more Sargents, visit the post on “warm and cool.”

Tomorrow: Taboret

Tuesday, January 29, 2008

Stroke Module

If you paint in oil with big flat bristle brushes, it gives the painting a kind of “big pixel” look. Here’s a plein-air study I did of some rooftops.

On the left is the actual painting, and on the right is a computer interpretation. The idea of the digitized version is to suggest the approximate module of the patches or brushstrokes. Each square is more or less equal to the width of the brush. So for a 16 x 12 inch painting, the brush was about a half inch wide.

I don’t think this painting was very successful. Part of the problem is that the units of detail are all about the same size throughout the picture. The effect is kind of clunky and simplistic, and there’s no center of interest. It’s like a whole symphony played at the same tempo and in the same key.

Let me propose this principle: a broad handling works better if there’s a center of interest in sharper focus.

You may have seen my painting of a McDonald’s sign before, but I want to make a different point with it. In the actual painting (oil, 10x8 inches), the word “McDonald’s” is painted as tightly and carefully as I could manage while standing outdoors in the parking lot.

But the line of writing below “McDonalds” is almost not readable. And the type on the yellow and red signboards lower down are just suggested with blocky shapes. In the background, the scale of blockiness increases even more.

In the mosaic version of the painting at right, I’ve interpreted the image in two sizes of tiles, with smaller tiles near the center of interest to make the simple point about varying the module of brushstrokes.

This principle of the scaling of detail is one of the hallmarks of the late 19th century portrait painters, like Sargent, Zorn, Sorolla, or Valentin Serov. Serov isn’t well enough known in America. Here is his portrait of the composer Rimsky-Korsakov. Click on it; it's a big juicy file, thanks to Wikimedia Commons.

Serov painted the face in relatively tight focus, but he represented all other areas of the picture with rough strokes made with a bigger brush module.

I find this orchestration of detail deeply satisfying because it captures the way our eyes actually perceive the world. There’s a tight focus at the center of interest, and bigger shapes in the periphery. Serov gives us all the information we need to understand the character of the man, no less and no more.

Look at this background detail from the Serov portrait. It has a wonderful “pixelly” abstract quality, like something caught at the edge of vision.

And here’s another detail, placed out of context next to the rendering of the face, and turned upside down to help us see them abstractly. Note that these two detail areas are shown at exactly the same relative scale of enlargement.

In context, the strokes effectively describe the clutter of papers on the desk. They don’t call attention to themselves as strokes or as paint. Instead they convey what they need to convey and then they keep encouraging the eye to return to the face and hands. If he had painted the outer areas with the same level of detail, the sense of immediacy would have been lost.

I call this scaling of brushstrokes the “stroke module.”

It’s a good general rule to strive for variety in the stroke module. Use a smaller stroke module (with smaller brushes or digital brush tools) for the center of interest, and then use bigger brushes and broader handling for the peripheral areas.

Tomorrow: Line and Wash

Monday, January 28, 2008

Inner and Outer Growth

When a tree grows each year, it adds some twigs and branches, but it also increases the girth of its trunk.

As artists we grow the same way. Our outer growth includes the practical skills of the hand: things like smooth calligraphy, accurate drawing, efficient color mixing, or an intuitive digital interface. We develop these skills from daily practice.

Our inner growth as artists has more to do with what we’re doing when we’re not actually painting. It includes our art historical awareness, our scientific understanding, our observational sensitivity, and our aesthetic taste.

That inner growth—the trunk of the tree—takes a lifetime to develop. If our roots are drawing inspiration throughout our lives, we can add a growth ring to our inner artistic selves, even if we are not practicing art daily.

This is encouraging news for people who are out of the habit with daily skills. You can keep growing as an artist even if you’re a busy parent with your art supplies languishing in the closet or a college student wrapped up in other concerns for a few years. As long as we keep seeing and thinking as artists every day, the trunk of the tree keeps growing.

On May 28, 2007, The New Yorker published the following about playwright Tennessee Williams:

"When, in late 1948, his play 'Summer and Smoke' failed on Broadway, Williams’ confidence dipped still further; he felt, he said, like a 'discredited old conjurer.' To his champion Brook Atkinson, the drama critic of the Times, he wrote in June 1949:

'The trouble is that you can’t make any real philosophical progress in a couple of years. The scope of understanding enlarges quite slowly, if it enlarges at all, and the scope of interest seems to wait upon understanding. . . . All artists who work from the inside out have all the same problem: they cannot make sudden, arbitrary changes of matter and treatment until the inner man is ripe for it.'"
All of which leads to a philosophical question that I’d like to pose to those of you who are teachers or students of art: What can or should an art school nurture? The inner or outer artist? Is it possible for a school to nurture both?

Painting above by Peder Mork Monsted (1859-1941), Link.
Thanks for the quote, Dave S.

Tomorrow: Stroke Module

Sunday, January 27, 2008

Color Wheel Masking, Part 1

Today I’d like to introduce an approach to color that I’ve been developing over the last 10 years. I’m very excited about it, and I'd love to know your reactions. I call it “Color Wheel Masking.” I’m going to show you a practical method that you can use to accurately describe any color scheme that you see.

Let’s start with the basic color wheel with the primary and secondary colors are arranged around the outside of the circle in the normal way. As each of these colors approaches the center, it becomes a neutral gray. Any individual color can be pinpointed on the surface of the wheel in terms of its hue and chroma (“chroma” is also known as “intensity” or “saturation”). For the moment, we’re ignoring value as a dimension of color.

If a single color can be charted on the circle, then it follows that the whole scheme can be charted, too. To chart an entire color scheme, it helps to think not only which colors are included in a composition, but also which colors are left out.

Let’s look at some actual pictures to see which colors are in and which are out of the color scheme.

On the left is a photo of some roses and leaves; on the right is a Christmas painting by Norman Rockwell. Each of these painting has greens and reds in different distributions. Both essentially lack yellow, orange, violet and blue.

Here’s another photo and painting paired together. What they have in common is blue and orange—but no red, no yellow, no yellow-green.

Here are two more pictures. Their color schemes are not identical, but basically they’ve got strong reds and yellows, some greens, and a dull blue-violet. What they’re both missing are full-intensity blues and greens.

Now let’s see if we can design a mask to fit over the color wheel to fit these schemes. We want the mask to show only the colors we see in the picture and to leave out the colors that are absent. The Rockwell painting is pretty easy, because it only includes greens and reds (plus a hint of blue in the package and very dull yellow in the ribbon).

The color mask here is a long diamond shape that includes the complementary colors that oppose each other across the middle of the wheel, leaving out everything else.

Here are the images with the blue-orange polarity, along with a masked color wheel. Note that inside this diamond shape, there are some other colors near the center: just a hint of red and a touch of yellow-green and blue-green. The colors inside the perimeter feel sufficient for a complete color scheme, even though we’ve left out a lot.

The mask doesn’t have to be this long diamond shape, because not all color schemes are complementary. Nor does it have to go all the way to the edges, because plenty of paintings lack full-intensity chromatics.

The mask can also be a small triangle in one part of the wheel. Here I’ve taken two paintings from Dinotopia: Journey to Chandara and mapped out their color schemes by digitally defining a shape on the wheel and ghosting the rest.

The swamp scene has dull yellow-greens and browns (browns are really dull oranges). The colors can be contained in the small triangle. The corners of that triangle never touch the edges of the wheel, because the painting doesn’t have any colors of full intensity. As you can see from the ghosted perimeter, the color scheme excludes blue, purple, and red.

Now all of a sudden we have a great way to describe any existing color scheme. But that’s just the first application of color wheel masking. Next Sunday I’ll show you a range of shapes for color wheel masks. Following that, I’ll describe exactly how to use color wheel masks to generate and experiment with color schemes.

In the intervening time, if you get a chance, I recommend that you can paint or digitally create your own color wheel to use as a tool for your own experiments.

Tomorrow: Inner and Outer Growth

Saturday, January 26, 2008

Lorrain Mirrors

For centuries artist have used darkened mirrors and smoked lenses to help them view a real landscape in simplified tonal values.

By the nineteenth century these optical devices became widely known as “Lorrain mirrors” or “Claude glasses.” Their darkened reflections suggested the work of landscape painter Claude Lorrain (1604?-1682). Lorrain himself, though, probably never used them. The name appeared long after his death, and for a time the devices were associated with the English poet, Thomas Gray (1716-1771).

Antique Lorrain mirrors were usually elliptical and slightly convex to allow the viewer to see the entire scene in miniature.
Here’s a simple homemade Lorrain mirror fashioned out of an ordinary piece of glass painted black on one side. The backside and edges were then protected with tape. In a pinch you could get the same effect by looking at the reflection in a lens of your sunglasses cupped in your hand.

For artists nowadays, the benefit of studying a darkened reflection is that it desaturates the colors, reduces the detail, and organizes the tones. By grouping the darks together into large masses, the vista takes on a romantic or picturesque aura. You can immediately see how to proceed with your tonal design. It’s easier to compare the relative brightness of light values—such as clouds compared to white buildings.

Here’s a photo manipulated with Photoshop to simulate the effect. I occasionally use Lorrain mirrors to help me choose a motif, or study it before commencing to paint. They’re also helpful for a mid-course check during the painting. They guard against the tendency we all have to lighten the values of the shadows, which results from our eyes adjusting to the dark areas and seeing too much detail in them.

If you prefer looking through a transparent viewer rather than seeing a reflection in a mirror, you can improvise your own Lorrain glass using a dark gray filter, a welding goggle, or an unexposed piece of film.

In an era before photography, both artists and tourists enjoyed the novelty of looking at real landscapes through gold- or blue-tinted Lorrain glasses. A heroine from an English play dating from 1798 said, as she peered through her warm-tinted glass: “How gorgeously glowing.” Then switching to a dark glass, she said, “How gloomily glaring.” Finally, looking through a cobalt-tinted glass, she exclaimed, “How frigidly frozen.”

For more:
Tintern Abbey Viewing Station with live Lorrain mirror webcam. Link.
Archived webcam shots show changes of light through the day. Link.

Final quote from Spectacles and Other Vision Aids: A History and Guide to Collecting, by J. William Rosenthal. p. 276,
Tomorrow: Color Wheel Masking

Friday, January 25, 2008


Tomorrow the Allentown Art Museum in Pennsylvania will open an exhibition of artwork from the National Geographic magazine. The show includes over a hundred paintings from the magazine’s 120-year history.

I’m very excited to have three paintings in the show, especially since the show contains the work of some of my all-time heroes, like Tom Lovell (see post on Lovell on the blog Lines and Colors).

One of my pictures shows the giant meat-eating dinosaur Giganotosaurus, which made a stir in the paleo universe because it was said to be larger than T.rex.

I met the Argentinian paleontologist Dr. Rodolfo Coria on October 7, 1994, a few short months after he had uncovered the bones, and before he had even come up with a name for the creature.

But even before I painted the Geographic piece, I did this rendering of Giganotosaurus for Dinotopia: The World Beneath (1995).

When it came to coloring the dinosaur I called Dr. Coria: “This is your dinosaur,” I said. “What color do you want him to be?”

“Color?” he replied. “That’s your problem.” So I took the artistic liberty of giving the dinosaur a bright color scheme to make him look as impressive as possible.

A year after The World Beneath was published, National Geographic asked me to do a couple of illustrations for an article on Argentinian dinosaurs. One painting shows the skull of Giganotosaurus compared with “Sue,” the famous giant T.rex.

Here’s a cast of a tooth from a Giganotosaurus.

The second painting shows Giganotosaurus running at a thundering pace. This time I used a slightly more conservative coloration. To accentuate the motion, I used shallow depth of field (see earlier post on the subject), blurring the distant trees, and kicking up a splash and a dust cloud from the feet.

This painting was done over ten years ago. Since then, John Hutchinson of Stanford University has convincingly argued that giant dinosaurs like T.rex or Giganotosaurus probably didn’t have the leg muscles to be able to run at the kind of speeds we imagine.

So if I were to do this painting again, I’d show him at a fast walk. A walking dinosaur may not be quite as impressive as a running dinosaur, but as long as he’s walking faster than his prey, it’s fast enough.

For more info:

  • YouTube video with interview clips of artists: Link.
  • Lines and Colors article on the exhibit:Link.
  • Art Department post by Irene Gallo: Link.
  • Allentown newspaper story: Link.
  • Related events: Link.
  • Collectible print available as part of Home Planet Portfolio. Link.

Tomorrow: Lorrain Mirrors

Thursday, January 24, 2008

Motion Blur

We took a look at speed blur on a previous post. Speed blur is what happens when a camera tracks along with a fast moving object, blurring the entire background along the path that the camera travels.

Motion blur is a little different. It’s what happens when a form moves rapidly in front of a stationary “camera.”

If you look at individual frames from live action films, any fast moving object has a softly blurred edge. The ability to simulate motion blur in CG animation was the revolutionary breakthrough that made the embryonic Pixar company take off in its first successful films. Very primitive CG animation, like traditional stop motion animation, left hard edges on moving objects, which gave a jittery rather than a fluid feeling to the motion.

As painters of still images—digital or traditional— we can take a lesson from these animation pioneers.

This oil painting from Dinotopia: First Flight (1999) shows dancers dressed up as dinosaurs parading at night through a city. They’re caught mid-stride in a wild dance. Their left feet are swinging forward, and their arms are flapping upward.

The faster the form is moving, the more it is blurred.

I painted in the figures and the background all wet together, and then softened all the edges in the direction of the line of action. For this kind of soft passagework, a slower drying medium helps.

To suggest that the “camera” was tracking along with the dancers, and to give a sense of shallow focus, I also blurred the details of the crowd across the street. If I had painted all these elements with crisp edges, they would have lost the feeling of depth and motion.

For more examples of motion blur in painting, have a look at the wildlife art of Manfred Schatz. Link.

Tomorrow: Giganotosaurus in Allentown

Wednesday, January 23, 2008

Mystery Artist Revealed

Radikin guessed it right: Today's painting called “Blossomed Furze” was by Beatrix Potter. Most of her famous books, like Peter Rabbit and Benjamin Bunny were based on her own pets by the same name. She carried them around with her on vacations and sketched them often.

Throughout her life she made many studies of mushrooms, flowers, animals, birds, landscapes, and interiors, which still set a high standard of observation, even among natural science illustrators.

She was a stickler for truth to nature. As much as she adored Wind in the Willows, she once offered this gentle criticism:

Kenneth Grahame ought to have been an artist—at least all writers for children ought to have sufficient recognition of what things look like—did he not describe “Toad” as combing his hair? A mistake to fly in the face of nature—a frog may wear galoshes, but I don’t hold with toads having beards or wigs! So I prefer Badger.”

Artwork and quote from The Art of Beatrix Potter, © Frederick Warne Co, 1955.

Tomorrow: Motion Blur

Mystery Artist

The first of you to name the artist who created this work gets a free deluxe map of Dinotopia and a 2-CD Audio Adventure of The World Beneath. One guess per person, please.

Tuesday, January 22, 2008

Virtual Reality, 1979

Back in 1979 there was no such thing as “virtual reality.” Heck, there was no such thing as a personal computer, either. Or computer animation, unless you count Pong, Atari’s hot new game.

But that didn’t stop my inner Leonardo from daydreaming about how we might interact with CG alternate universes.

At the time I was an anthro major at UC Berkeley. According to my sophomoric prognostication, we would someday be able to enter “a world of pure illusion, utterly free from danger, into which one can actually walk and explore!”

Here, for your amusement, is “Vision Quest,” my 1979 prediction of what was supposed to come. Wasn’t the future fun back then? So why hasn’t it gotten here yet? Click to enlarge any page.

The headpiece unit:
Field size and sound:
Alternate reality:
Off a cliff:
Your friend the 8-ball:

Tomorrow: Mystery Artist

Monday, January 21, 2008

Gurney Journey in Eastpointe

Fans of Gurney Journey will be interested to know that, in the words of Detroit Free Press reporter Kim Shine, "The Gurney Journey takes place from 11 a.m. to 1 p.m. Saturday.”

If you go to Eastpointe, Michigan's Art and Ice Festival next Saturday and Sunday be sure to check out the gurney races. These events “have team members pushing one another on wheeled stretchers. The event is open to any four-person team that wants to race through an obstacle course for a $40 donation per team." Link.

Elegant Graphics

In his book The Visual Display of Quantitative Information, Edward Tufte offers this graphic by Charles Minard of the depletion of Napoleon’s troops during his disastrous march to Moscow in 1812 as an example of the principle that “graphic excellence is that which gives to the viewer the greatest number of ideas in the shortest time with the least ink in the smallest space.”

Among other things, Tufte’s books have presented an ardent case against the mind-numbing way that people use PowerPoint to communicate information in business and education. Link.

Tomorrow: Virtual Reality, 1979

Sunday, January 20, 2008

Is Moonlight Blue?

Moonlight is about 400,000 times weaker than direct sunlight. It’s so dim that the color receptors in our retinas, called the cones, can barely function.

In moonlight the other retinal cells called rods are doing most of the work. Rods detect relative lightness and darkness, but they are entirely color-blind.

Moonlight is simply the white light of the sun reflecting off the gray surface of the moon. There’s nothing in that interaction to give the light a bluish or greenish quality. In fact, scientific instruments have shown that the light from the moon is very slightly redder in color than direct sunlight.

These facts added together suggest a mystery at the heart of how we as artists choose to portray moonlight in paintings. If moonlight is just gray-colored light, and if it’s close to the minimal threshold of our color receptors anyway, then why do so many artists paint moonlight as bluish or greenish? Do we really see it that way? Is it some kind of illusion, or perhaps is it just an artistic convention?

Let’s look at some paintings by master painters of moonlight. As you look at them, consider your own perception of the colors at night, and ask yourself which of the paintings best convey your own experience.

Here’s a painting by J.M.W. Turner. It’s fairly gray, with just a hint of warm color around the moon. Notice that there isn’t much detail in the shadow area. All you really see clearly are the silhouettes of the sail and the boat on the water.

Russian seascape painter Aivazovsky painted this night scene lit by a golden moon. The sky, the water, and the shadows all sink into blue-green tones. He doesn’t show very much detail, and he stops well short of black in the shadows.

This lightening of darks was also a feature of Remington’s nocturnes. The cast shadow to the left of the pony’s nose is composed of dull umbers and greens. These luminous shadows lighten and liven the obscurity. Except for the light saddle cover, Remington has left most of the edges soft and undefined, especially on the donkey on the right.

This famous nocturne by Whistler of the Battersea Bridge uses a fairly saturated blue-green color, especially in the water and in the silhouetted figure. The detail is blurred throughout, even in the areas where the bridge appears against the sky, setting up for the tiny sparkles of light in the distance.

One of the reasons for softening the edges is that we depend on the cones for fine discrimination of edges. Unfortunately the cones are located on the fovea, the centerpoint of vision, and with them off-line in the darkness, we just can’t sort out small details.

If you take a book or newspaper outdoors in moonlight, you can see that there is writing on the page, and you might be able to read headlines or other large type, especially when you glance around with your peripheral vision. But reading normal size text is almost impossible. When you look directly at the words, the blind spots get in the way.

I said earlier that our cones are barely functioning in moonlight. In fact, contrary to what some authorities have claimed, most people’s cones can make basic color judgments by the light of a full moon. But how much variation in color can we really see?

Maxfield Parrish rendered this moonlight scene with quite a bit of color saturation. He painted the yellow moonlight, the reddish cupula on the barn, the deep blue of the sky, and the orange color on the shadow side of the house. Did he really see such colors in moonlight, or did he invent them for pictorial effect? Too bad he’s not here to ask.

Direct plein-air painting is virtually impossible in moonlight. Every artist has to work from memory and imagination. We may try to convey our actual optical sensations, but we’re not scientists. Each of us is also trying to make a subjective aesthetic statement intended to evoke a particular mood or emotion. Any moonlight painting is an attempt to translate a “rod experience” into a “cone experience,” an image that will be seen in a brightly lit environment.

Here’s how you can test how your cones actually respond to color in moonlight. Paint a set of separate, matching, unmarked color swatches or find some construction paper at about the same value. Take them into full moonlight (this Tuesday) and let your eyes adjust (it takes about 30 minutes). Shuffle the cards, and while you’re still outdoors, mark on the back what colors you think they are.

I have used Photoshop to manipulate a photo of the swatches (actually shot in daylight) to simulate how they appeared to me under the full moon: dulling, darkening, and blurring them. Both Jeanette and I could easily identify the basic hue family of each swatch. But beyond that basic classification, we weren’t sure, and the gray swatch confused us both.

When I looked at the same swatches in the much dimmer light of a half-moon, or in a moon shadow, I found my cones went sub-threshold and shut down completely, and the swatches became completely monochromatic.

Although the rods of the eye can’t actually see color, scientists have shown that they are most sensitive to greenish wavelengths of light. As a result blue-green hues appear lighter in tone in dim conditions. There’s a name for this: the Purkinje Shift. It’s a different phenomenon from, and often mistaken for, the perception of moonlight as blue.

You can demonstrate the Purkinje Shift by comparing a red and green swatch that start out indoors at the same value. If you take them outdoors in moonlight, the greenish one will seem much lighter in tone. Many observers have noticed that red roses look black in the moonlight.

If you scroll back up to my Photoshopped version of the moonlight color swatches, you can see I’ve adjusted the values to simulate the way the red and green looked to me as a result of the Purkinje Shift.

Here, Remington shows a scene with Indians in moonlight. We see their flesh tones and some clear red touches in their costumes. Throughout, the edges are much crisper than his other painting.

This nocturne of old Cincinatti by contemporary artist John Stobart has a distinctly bluish cast. He introduces much more detail than we’ve seen in the other examples, reminiscent of the “day-for-night” film shoots in old westerns. You can even read the name “Bonanza” on the shadow side of the ship.

In addition to the moonlight, there’s a secondary source of yellow-orange lamplight. In this case, one could argue that the blue cast to the picture may be a complementary color induced in opposition to the color of the lamplight.

Atkinson Grimshaw was famous for his poetic moonlight studies. Here the shadow masses at the left are fairly soft and impenetrable, but the bricks and branches show up very clearly. The moonlight on the road is an intense yellow-orange, assuming this reproduction is accurate. The shape of the patch of light points to the lovers standing in silhouette at left.

Russian landscape realist Ivan Shishkin, painted this haunting image of a winter night in the wild north. The snow in moonlight is relatively brilliant, with a soft halation along the edge at left, but it’s not yellowish. The cast shadow gradates in tone, getting lighter as it catches more sky fill and bounced light. There’s quite a bit of detail in the tree form, but he has kept the foreground and background description to a minimum.

So, to get back to the question posed earlier, why do we see moonlight as blue?

Saad M. Khan and Sumanta N. Pattanaik of University of Central Florida have proposed that the blue color is a perceptual illusion, caused by a spillover of neural activity from the rods to the adjacent cones.

A small synaptic bridge between the active rods and the inactive cones touches off the blue receptors in the cones, kind of like an insomniac turning over in bed and rousing his sleeping spouse.

This influence of rod activity on the adjacent cones tricks the brain into thinking we’re seeing blue colored light, even though we’re really not.

As the authors put it: “We hypothesize that the rod cells predominantly synapse onto the S-cone (cone cells sensitive to bluish light) circuitry resulting in the visual cortex perceiving a tinge of blue.”

So moonlight isn’t blue; our eyes are just playing tricks on us.

Unfortunately, this tantalyzing hypothesis remains untested. I contacted Dr. Khan and he told me that because of other projects he hasn’t had time to prove the hypothesis in controlled conditions. I hope that he can shed more light—of whatever color—on this elusive topic.

Until then, moonlight remains a mystery at the meeting point of art and science.

Further reading:
  1. Khan and Pattanaik’s summary article in Journal of Vision, 2004. Link.
  2. Related discussion on the NASA web site. Link
  3. "The Eye and Night Vision," from American Optometric Association. Link.
  4. More on Remington’s nocturnes at David Apatoff's blog. Link
Tomorrow: Elegant Graphics