These talks are almost always informative, entertaining and brain-ticklingly thought provoking. Some are on art (see my post on The Face of Leonardo?).

In this particular talk, Lotto utilizes several familiar but striking optical illusions (see my previous posts on some of them here and here), plus a few others, but goes beyond the usual concerns of the mechanics of vision into the questions of why we see as we do, why these particular illusions work, and how the way we see functions in our adaptation to the world.

The LottoLab site includes some articles and features on related subjects.

Much of the talk is about the nature of color, and in particular about a point that I often mention as perhaps the single most important thing I have ever learned about color, color mixing and color perception — that context is everything.

In his Glass Microbiology project he has created a series of glass sculptures of viral structures, to, in his words, “contemplate the global impact of each disease and to consider how the doctoring of scientific imagery affects our visualisation of phenomena”.

The sculptures are of viruses that are associated with particularly virulent and well known diseases, Smallpox, HIV, SARS, Swine Flu and, in the case of the image above (with detail below), E. coli.

The fact that the virus sculptures are made of glass, a transparent substance which, in its most basic form, has no color of its own, is indicative of the second aspect of Jerram’s investigation, the suggestion that the coloring of scientific images carries implications beyond conveying information.

It’s common for scientific images to be given false colors for the purpose of clarity, or easy perception of information that may be hard to glean in the images’ “true” state. An example of this might be the application of false colors to astronomical images to display the structure of nebulae or the light from infrared or radio sources.

It is also common to color images of viruses; in fact a majority of illustrations and images of viruses that are not the original electron micrographs seem to be intensely colored. Jerram speculates that as a result, most non-scientists might assume that real viruses are actually brightly colored.

He further speculates that the practice can promote a sense of wonder and and make the images more impressive (possibly intentionally), as well as carrying an emotional tone, perhaps one of menace.

The glass sculptures neatly obviate the effect of color (except for one that was deliberately colored by a photographer, though it acts as a contrast), and reduce the viral shapes to just that: their shapes.

Jerram has another interest in removing the effects of color and judging the effect on perception; he himself is colorblind (an awkward term that might more accurately be called limited spectrum color vision), though I don’t know in what range his limitation extends.

The play of light on these sculptures, however, is still beautiful, and the perception of the shapes is heightened by the refractive characteristics of glass (something I respond to as strongly visually appealing); so I have to submit that Jerram has removed one source of intentional visual appeal only to substitute another.

However, as sculptures they work wonderfully. The shapes of viruses are particularly fascinating forms. I also find it compelling that microscopic structures capable of being deadly on a devastating scale can be represented with such beauty.

Jerram’s glass sculptures will be highlighted in a solo show at Smithfield Gallery, London from 22 September to 3 October, 2009.

[Via MetaFilter]

All of my studies of color and color theory have led me to the inexorable conclusion that the single most important rule of color is that the human perception of any color is almost entirely dependent on adjacent or surrounding colors.

This is the basis of Eugene Delacroix’s wonderful quote: “I can paint you the skin of Venus with mud, provided you let me surround it as I will.”

While this principle is visible to the trained eye, both in painting and in life, it is never made more clear than in deliberately created optical illusions, like the e-Chalk color perception illusion I wrote about in this post.

This image shown here is one of the most striking illustrations of this principle I’ve seen.

I came across it in a post by Phil Plait on Bad Astronomy, who indicated the the original is from Akiyoshi Kitaoka’s optical illusion website (scroll to the bottom of the page).

Anyone with normal color vision will see a series of green and blue spirals. There would be little chance that a casual observer would suggest that the blue and green might be the same color, and yet they are.

You can see in the first detail image that the “green” spirals are only crossed by bands of orange, and the “blue” spirals are only crossed by bands of magenta.

In the second detail, you can see the Photoshop foreground/background color blocks where I have used the Eyedropper tool to pick one color out of the “green” band, and the other out of the “blue” band.

They are identical RGB values, 0, 255, 150. The same color.

The color is actually a green leaning toward blue. Richard Wiseman used Photoshop to change all of the values except the green and blue bands to black, and you can see a detail of the result in the bottom image. There is also a simplified version of the illusion here.

So the next time you’re looking at a color an think “that’s green” or “that’s blue”, well, maybe it is, maybe it isn’t, depending on the surrounding colors.

California born artist John Pugh paints large scale trompe l’oeil images, usually on the sides of buildings, that reveal impossible, and often amusing, dimensions to an otherwise flat wall.

In his Mana Nalu (power of the wave) Mural Project (image above, top, large version here) in Hawaii, the flat side of a building appears to be deeply concave, and filed with an enormous cresting wave, in which we see a personification of Queen Lili’uokalani. Riding the wave is pioneering surfer Duke Kahanamoku, and standing at the foot of the wave, looking for all the world like real children walking on a ledge in front of the oncoming wall of water, are three painted children.

Pugh likes to give our sensibilities an extra tease at times by including a painted observer in his illusionary scene.

In his Siete Punto Uno in Los Gatos, California (image above, bottom, large version here), a red jacketed woman peers into an apparently earthquake caused break in the wall of a cafe, that reveals a hidden temple of the Mayan Jaguar God (the bringer of earthquakes in their mythology).

Pugh’s web site showcases his mural work, public and residential and corporate. It also includes a page of “mural mishap” accounts, in which the illusion of the murals has prompted amusing responses from people, such as patrons in a bar who break glasses trying to set them on trompe l’oeil “shelf”, or people who walk into walls trying to walk “into” his paintings, a la Road Runner cartoons.

In addition to his site, Pugh maintains a site for prints and mural posters that also has galleries of images.

[Via Daily Mail Online]

He suggests that this is more than having a background knowledge of the artists or particular paintings, and in fact has to do with physical proximity to the painting, a reference to a kind of “sweet spot” from which the painting was intended to be seen, particularly in terms of being close enough to the image for it to fill a significant part of your visual field; but also, in some cases, requiring a vantage point from one side or the other.

A case in point is Daniel Vosmaer’s Delft from an Imaginary Loggia (image above, top), which looks “off” at first, but apparently resolves into a strikingly naturalistic scene when viewed from a position close to the bottom left of the painting. Some are more natural seeming in appearance when seen from a distance or in reproduction, like Adriaensz Berckheyde’s The Grote or St. Bavokerk in Haarlem (image above, bottom), but still evidently reveal their full force only when seen up close.

Gopnik goes on to suggest that over half the paintings in the show, and many other Dutch cityscapes, interiors and even still lifes, are meant to respond to an off-center point of view.

It’s a fascinating idea, and one I hope to put to the test by traveling to see the show.

When I first looked at the slide show in the Post of images from the exhibition, I was ready to jump in the car and drive down, because it looked as if Vermeer’s beautiful View of Delft (larger image here) was among the paintings on exhibit. I saw this amazing work when it was at the wonderfully extensive Johannes Vermeer exhibition at the National Gallery back in 1995, and I have been dying to see it again since. Unfortunately, that work was only part of the current exhibition in its other venue, the Royal Picture Gallery Mauritshuis, which is home to the painting. Apparently the curators at the Maruitshuis felt it was too dangerous to allow the large painting to make the trans-Atlantic voyage again, as explained here.

Still, the current exhibit of Dutch cityscapes, from the height of their glory, should be something to see indeed. The exhibition contains 48 paintings by over 40 Dutch masters, including Gerrit Berckheyde, Aelbert Cuyp, Jan van Goyen, Jan van der Heyden, Pieter de Hooch, Hendrick Vroom, Pieter Saenredam, and Jan Steen; and is supplemented with maps, atlases, illustrated books and prints.

Pride of Place: Dutch Cityscapes of the Golden Age is on display at the National Gallery in Washington until May 3, 2009.

There are several types or projections, the most familiar are “perspective projection” (traditional linear perspective), in which lines drawn from the sides of parallel objects converge on vanishing points, and “oblique projection”, in which those lines remain parallel (the “Sim City” look).

In any of them it is possible to create an image that superficially seems reasonable, but would actually be impossible as a three dimensional object. Many of us are familiar with these in the form of traditional “optical illusions” and in the graphics of M.C. Escher.

Andreas Aronsson is, in his words, a “Professional IT‑technician. Spare time multimedia experimenter. In Sweden.” He has a fascination with impossible objects, and regularly posts his own playful “Impossible Figures” to his blog.

These often take the form of objects (usually done in perspective projection) with shared sides or lines of connection that defy real-world geometry. They make for fun visuals; and examination of them generates a playful brain-tickle that gives us pause to reflect on the nature of the visual presentation of objects, what we take for granted and how easily our eye can be fooled into accepting the three dimensionality of lines in a two-dimensional surface (even if that surface is a screen).

You can flip through the posts on his site tagged with “Impossible Figure“. You can also read his page “About Impossible Figures” in which he talks about his fascination with them and his working process in creating his images.

[Via Neatorama]

The term comes from the Greek anamorphoun, to transform. Anamorphic images have a long history in art. The earliest examples in Western art are found in Leonardo’s notebooks, though anamorphic images may have been developed in Chinese art around the same time.

Anamorphic perspective was employed in the illusionistic painting of church vaults, like those of Andrea Pozzo (image above, top, large version here) and Andrea Mantegna, but it has most often appeared in art as a curiosity or entertainment; or been used for the creation of hidden or secret images, requiring a matching mirrored surface to reveal their true nature.

Anamorphic images can be of as much interest to scientists as they are to artists, as NewScientist reports in their mention of a recent seminar on technical aspects of anamorophic art at the London Knowledge Lab; and an event at the National Gallery in London called Curious Perspective: Anamophosis in Art.

The NewScientist article is accompanied by a slideshow of anamorphic images.

The event at the National Gallery in London centered on the wonderfully enigmatic painting The Ambassadors by Hans Holbein the Younger, which is in their permanent collection. I devoted a post to The Ambassadors in 2006.

One of the notable modern applications of artistic anamorphosis that is missing from the NewScientist article (and many other resources) is the use of anamorphic images in sidewalk art, as exemplified by the work of Julian Beever and Kurt Wenner.

You can also add to the list the illusionistic point-of-view dependent paintings of Felice Varini and the modern continuation of traditional anamorphic art by István Orosz (image above, bottom). I’ve gathered some other anamorphic art resources below.

[NewScientist article link via Digg]

You may have noticed when looking at photographs of small objects, models, dioramas or model train layouts, that there is a limited range of the scene that is in focus. This is due to the limited focal length of camera lenses when focused at short distances.

A fascinating practice that has become popular in the last couple of years is “tilt-shift photography”, the use of techniques involving tilting the lens relative to the plane of the scene, often from a high vantage point, mimicking the way small objects are often photographed from above, and using a large aperture (lens opening), creating a shallow depth of field, to produce photographs of real scenes and objects that look like miniatures.

There is a good selection of this kind of photography in a recent article on Smashing Magazine that serves as a nice introduction to the phenomenon if you haven’t encountered it before; and a resource for further investigation if you have. The article also includes some tilt-shift videos and some links to related resources.

It’s uncanny how strong the effect can be. Even when you know the scenes or objects are real, it’s difficult to shift out of the perception that you’re looking at objects in miniature.

Something to think about the next time you’re tempted to refer to a realist painting as “photographic”.

[Images above: Tiltshiftphotography.net and Tilt-Shift Photography: It’s A Small World After All]

Web Urbanist has posted a nice overview, Amazing 3D Art from the Best Street Artists, with a selection of work by Wenner (image above), Beever, and others; including Edgar Muller and Manfred Stader, Tracy Lee Stum, Eduardo Relero, Rod Tryon and Anthony Cappetto, giving you a quick look at some highlights of this apparently growing phenomenon. It also features muralists like Grohe and Greg Brown, and even a 3-D graffiti artist known as Diam.

Some of the pavement chalk art takes the form of large scale reproductions of famous works by artists like Da Vinci, Vermeer, Rembrandt and others.

Much of the work that has made this a phenomenon is based on anamorphoses, images that are distorted in such a way that they only look “right” form a certain vantage point. The limitation is a trade off for the illusionistic power the images can have to appear three dimensional when seen from that viewpoint. You can see an example of how this works here.

Anamorphosis has been used in art for centuries; you can see a particularly striking example of it in Hans Holbien the Younger’s famous double portrait The Ambassadors, which contains the anamorphic apparition of a skull.

The new urban sidewalk artists have used this approach to create images of objects and environments that, when viewed from the correct vantage point, appear to extend above or below the pavement on which they are painted.

Wenner has gotten new, upscale website since I wrote about him, casting himself as available for corporate commissions and highlighting his architectural designs. Beever is still coasting along like a street artist, with a homemade looking, 90’s style site, but he has added additional images.

Wenner’s site includes some videos of him working, and there are some others on YouTube of a short documentary, Masterpieces in Chalk.

If you look around, you’ll find a few not covered in the Urbanist article, like Cuong Nguyen.

Muralists like Grohe or Brown are in the long artistic tradition of “trompe l’oeil” (French for “trick the eye”), in which artists have created images that appear to have dimensionality beyond the surface on which they are painted, relying less on anamorphosis and more on realism. This tradition includes some of the fantastic dome paintings in which the vault of heaven, filled with angels and religious figures floating in apparent disregard for gravity, is projected on the interior of a dome.

Of course, if you step back and think about it, the modernists were right; all representational art is an illusion.

As part of the Gutenberg-e project by the American Historical Association and Columbia University Press, Sarah Lowengard has written a scholarly treatise on The Creation of Color in Eighteenth-Century Europe, the third chapter of which, Number Order, Form, delves into the history of color wheels and other visual systems of ordering and visualizing the relationships of colors.

The link going around the web currently (I found it on Digg) is to a post on the Color Lovers blog, which has extracted selections from her paper into an article on the History of the Color Wheel.

Color circles have been used to describe associations of colors from medieval times, but the first known example of the representation of hue in the form of a wheel, or circle, commonly suggested as the original color wheel, is traced to Sir Isaac Newton; whose keen mind was for some time focused on the nature of light and color.

Other systematic visual arrangements of colors precede it, like Tobias Mayer’s Trhchromatic Graph [correction - see below], which he first described in 1758 (interpreted by Georg Christoph Lichtenberg, image above, top left), but Newton’s circle is recognizable as the predecessor of the one in modern art texts. (For a couple of color wheels that I find particularly useful, see my links to Bruce MacEvoy’s artist pigment color wheels on handprint at the end of this article.)

Newton’s experimentation splitting sunlight with a prism is relatively well-known. (It’s still a fun and instructive practice is you haven’t indulged in it, I got mine from Edmund Scientific.)

Less well known is Newton’s original color circle, or hue circle, which was actually a kind of pie-chart (image above, top right), in which the bands of color he observed were distributed in wedges corresponding to their width in the observed spectrum, and arranged around the circle in the order of their wavelength. Newton emphasized that his circle represented the properties of the color of light (additive color), not artists’ pigments (subtractive color).

It was Newton who accomplished something that I have long been fascinated with, and confused by — the “closing of the circle”.

Physical wavelengths of light, which our eyes and brains interpret as different hues, can be thought of a part of a linear arrangement, segments of the electromagnetic spectrum; a continuous band of wavelengths of energy from the very short (X-rays and Gamma rays), with wavelengths measured in the distances equivalent to atomic nuclei, to the very long (radio waves) with wavelengths measured in distances on a human scale (meters or 10’s of meters).

The spectrum of visible light sits somewhere in between, at wavelengths the size of protozoa (micrometers, or millionths of a meter, also known as microns), ranging from red on the short end at 700nm, to violet on the long end at 400nm.

But how, my fevered little brain would like to know, does this linear relationship bend back on itself, like the optical equivalent of a Möebius strip, and connect in a continuous band; and how does it fit into that neat and oh-so-convenient system of primary, secondary and tertiary colors, triads; and in particular, the dramatic, and apparently biologically founded, relationship of color wheel opposites, or complementary colors?

This seems to have something to do with a “gap” in the color wheel, between the physical wavelengths of red and violet, in which the purples fill in with colors that are not discrete frequencies on the spectrum, but combinations of others.

I have to admit that I’m still basically unclear about this, but let’s face it, we always knew purple was weird.

Correction and addendum: Divid Briggs, author of The Dimensions of Color, was kind enough to write a comment and point out that though many systems of color charts precede Newton, Mayer’s was not one of them.

He also appears to have an answer to my question about the “closing of the circle”, which comes from the opponent model of vision. He explains if briefly in his comment on this post, and in more detail on The Dimensions of Color.

It turns out that I’m obliquely familiar with this model of human vision, which is based on two “channels” or scales of color, redness vs greenness and yellowness vs blueness, and a lightness scale or channel, in that this is the color model on which the LAB (CIELAB) color space is modeled.

CIELAB (”LAB color”) is a color space used in Photoshop, and is the fundamental color space on which Photoshop bases its interpretations of other color spaces. If you convert between CMYK and RGB, for example, Photoshop converts to the first color space to LAB and then from LAB to the other. (Here’s Adobe’s Technote.)

The CIELAB color space, based in part on Munsell but founded on the biological way in which the cones in the eye react to color, was codified in 1931 by the Commission Internationale d’Eclairage (International Commission on Illumination) to describe all colors visible to the human eye.

The closed circle of the color wheel is a product of the related opponent model of vision in which the interaction of the redness to greenness and blueness to yellowness scales forms a circle, and the oppositions produce the famous complementary color effects with which artists are so familiar.

So there’s my answer. It’s in the eye of the beholder.