Month: April 2019

A matter of perspective

Although I like to think of myself as a multitalented “Renaissance man” of sorts, I must admit that when it comes to drawing and painting, I have absolutely no ability. I’m truly pitiful at Pictionary, and I couldn’t paint my way out of a paper bag. Or so I’ve always thought. Based on what I’ve learned about the methods of some famous painters, I could probably produce some fantastic art from the inside of a very large paper bag, as long as it had a pinhole on one side and pretty bright light outside. All I’d have to do is trace the image projected by this primitive camera obscura. According to a controversial theory, this technique—or something very much like it—gave some world-renowned artists a little help as far back as 1420. Then again…maybe not. Getting to the bottom of this puzzle has been the consuming passion of quite a few artists, historians, and optical engineers.

Without a Trace

Tracing over a projected image is a straightforward notion, but if you’ve ever tried it (as I have) you probably discovered that getting good results is not as easy as it sounds. The easy part is getting the proportions right. But lots of things in any image lack well-defined borders, and trying to make sense of textures and the effects of light and shadow while tracing something is quite a complex undertaking. If, instead of tracing, I were painting, the challenge would become even greater, as I’d have to carefully match gradations in color—and as soon as I applied a dark paint to the light surface, the image in that area would virtually disappear. All that to say: projection or no projection, producing a convincingly realistic drawing or painting takes a lot of skill and practice. So if it turned out that one of the great masters from centuries ago really did pull this off, I’d be no less impressed by the final product—and more impressed by the artist’s cleverness.

We know that numerous artists nowadays, and over the past couple of centuries, have employed just such a technique; many of Andy Warhol’s best-known pieces, for instance, were done this way. Prior to the invention of photography, though, the only images that could be projected were live representations of the real world. The technology to do this, the camera obscura, has been known for many centuries—possibly since as far back as the fifth century BCE. If a tiny hole is placed in the wall of a very dark room and the light outside is bright enough, an inverted image of the outside scene is projected onto the wall inside. But the image is usually fairly dim and fuzzy. Two important innovations in camera obscura design occurred in the 16th century: the addition of a lens (which made the image sharper) and a mirror (which could direct the image onto a horizontal surface rather than a wall). And there are a few scattered records from the mid-16th century of artists suggesting the use of a camera obscura as a drawing aid, though the earliest confirmed date of anyone actually doing so is 1603.

An Obscura Artist

It should therefore come as no surprise that an artist might have used such a technique in the 1660s, and that’s just what some people have claimed for more than 100 years about Dutch artist Johannes Vermeer (1632–75). These suggestions first surfaced when people began noticing that the proportions in Vermeer’s paintings didn’t match those of other works from the time, in which the subjects were typically painted at the size the artist perceived them to be. But in Vermeer’s works, objects and people closer to the foreground are larger than those in the background—seemingly in just the proportions that they would be in a photograph—or a tracing from a camera obscura image. Several other clues in the geometry and lighting suggested the same thing, but there was no evidence that Vermeer actually had (or even had heard of) a camera obscura. In addition, since the scenes in question were interiors, presumably any image created by a camera obscura would have been incredibly dim. So for many decades the debate continued.

Then in 2001, architect Philip Steadman described in his book Vermeer’s Camera detailed research into the geometry of several of Vermeer’s paintings—backed up with photos of painstakingly recreated miniatures of the rooms from the paintings. Steadman’s studies showed that given the dimensions of the room in each scene (which he carefully calculated) and the viewpoint and size of each painting, all are absolutely consistent with an image of the room being projected onto its back wall with a camera obscura. In other words, given not only the uncanny accuracy of the paintings but also the specifics of their perspective, Steadman felt it was nearly a mathematical certainty that Vermeer partitioned off a small corner in the back of this room as a camera obscura and painted over the image on a canvas that hung on the wall. (In at least some cases, X-ray evidence shows that although there was no underlying sketch, there was a monochrome image beneath the color paint; this makes sense considering the very dim conditions inside the camera obscura.)

Tim’s Vermeer

In 2013, the story took another big step. Inspired in part by Steadman’s work, an inventor named Tim Jenison set about to recreate one of Vermeer’s paintings. Jenison claimed no artistic talent, but he did know a few things about optics. So he devised a mechanism that would have been entirely possible using 17th-century technology: a combination of a camera obscura and a small mirror positioned at an angle above the canvas. Using this setup, along with a room designed to be an exact duplicate of the one in Vermeer’s “The Music Lesson” (including live models in period dress), Jenison spent seven months creating his own version of a Vermeer. The striking results strongly suggest that Vermeer used a similar setup himself. The entire project was documented in the film Tim’s Vermeer, directed by Teller and produced by Penn Jillette (of Penn & Teller).

Both Steadman’s book and Tim’s Vermeer met with a certain amount of controversy, not least because they seemingly suggest that Vermeer did not produce his works with artistic skill alone. (Oh, the horror to think that he might have supplemented his considerable artistic skill with technological skill!) But the evidence from both sources is pretty convincing—and, of course, it mainly confirms what a lot of people had suspected all along.

Mirror, Mirror

Shortly after Vermeer’s Camera was published, another book hit the shelves that made much broader (and more controversial) claims—and also influenced Tim Jenison’s work. Painter David Hockney, in his book Secret Knowledge, alleges that European artists used optical aids for painting as early as the beginning of the 15th century. But rather than using a camera obscura, Hockney believes these artists used a concave mirror to project an image onto the canvas; no documentary evidence exists simply because they all chose to keep it a carefully guarded trade secret. Among the many artists on Hockney’s list are Van Eyck, Caravaggio, and Lotto.

Hockney noticed that around the early 1400s, paintings began to show a much more natural representation of light and perspective—that, in some cases, they looked nearly photographic. He was convinced that the level of realism and accuracy they displayed was simply too great to have been done by eye, so he started looking for other explanations. As he went back through history, he noted the use of the camera obscura and other optical aids, and he suspected that the practice may have been much older. He formulated a series of theories about how various works of art over a period of several centuries may have been made by using optics of one kind or another.

Experts in the art world are still divided over Hockney’s claims. Because his theories are so wide-ranging, some of them are bound to be accurate to one extent or another. But many critics believe Hockney has gone too far, and a few have spent considerable effort rebutting his theories. David Stork, a physicist and art historian at Stanford University, has published numerous papers debunking various aspects of Hockney’s book. Stork found alternative explanations for many claims of optical aids, pointing out that none of the available evidence requires one to posit the use of optics in the oldest and most controversial works; there are other, simpler explanations. In addition, Stork finds it highly implausible that the artists could have discovered, created, and kept secret such advanced technology for so many years.

Having read lengthy articles about this debate until my eyes blurred, I feel I have enough information to reach my own conclusion. And that conclusion is: it doesn’t matter. What Hockney, Stork, and I agree on is that even if these legendary masters did use optics, that does not in any way constitute “cheating”; they would simply have been tools of the trade. In the end, I think the years invested in this intellectual exercise might have been more profitably spent painting.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on May 21, 2005.

Image credit: unknown illustrator [Public domain], via Wikimedia Commons

It seems like every few days I run across yet another news story about a privacy catastrophe of one kind or another. Maybe it’s a huge corporation that suffered some sort of data breach, revealing private data about millions of customers. Or slimy behavior by social media companies like Facebook and Twitter. Or the latest creepy attempts by advertisers to track people’s movements across the web without their permission. Or any of countless other examples of how using the internet puts your personal information—and perhaps even your physical safety—at risk.

Online privacy is a hot mess these days, and with few exceptions, the big tech companies are working against greater privacy protections, not for it. It’s enough to drive even tech experts (to say nothing of the rest of us) to despair. That’s why I wrote Take Control of Your Online Privacy—I felt the world needed an easy-to-read summary of what the threats are and how ordinary people can achieve a reasonable level of privacy online without abandoning all technology and heading off to live in a cave somewhere. This book tackles web browsing, email, digital payments, social media, file sharing, and numerous other types of online activity, showing users of any platform what they can do to protect their private data. The brand-new fourth edition, released last week, brings the book fully up to date with all the latest techniques, hardware, and software you can use to keep your personal data private. I hope you’ll find it helpful!

This book, like all Take Control titles, comes as an ebook, and you can download any combination of formats—PDF, EPUB, and/or Kindle’s Mobipocket format—so you can read it on pretty much any computer, smartphone, tablet, or ebook reader. The cover price is $14.99, but as an Interesting Thing of the Day reader, you can buy it this week for 30% off, or just $10.49.

The national beverage of Argentina

I’m a coffee person. I wouldn’t say I’m addicted to it, but I do certainly enjoy drinking it on a more or less daily basis. Sometimes two or three times a day. In fact, now that I think about it, I could use a cup right now. Excuse me. (Time passes.) Ah, that’s better. I do not drink coffee for my health, although I am aware of studies suggesting that coffee consumption in moderation may reduce the risk of colon cancer, kidney stones, heart disease, and even Parkinson’s Disease. But I certainly appreciate the caffeine, the aroma, and the soothing effect of a warm beverage sliding across my tongue and down my esophagus.

Many of my friends, however, are tea people. I have nothing against a nice cup of tea now and then, and of course tea ably fills that hot beverage need. But in terms of aroma and both psychological and physiological impact, tea just doesn’t do it for me. Once again, tea’s supposed health benefits—of which there are, I admit, far more than those of coffee—don’t quite tip the scales. Maybe I’d be 5% healthier if I switched from coffee to tea, but then, maybe I’d also be 10% grouchier.

A Drink to Die For

I am always, however, happy to try new and unusual hot beverages, especially if they are reputed to have health benefits, a strong aroma, and a flavor frequently referred to as an “acquired taste.” And even more so if the beverage must be prepared and served in a highly ritualized way using special, single-purpose gadgets. So on a trip to Argentina in 2004, I was enthusiastic about sampling mate, their national beverage—and acquiring the necessary paraphernalia to make it myself.

Now, keep in mind: back then, mate wasn’t really a thing in the United States. This was long before every supermarket, convenience store, and cafe in North America hopped on the yerba mate bandwagon, with all manner of hot and cold drinks based on this plant. But even if you’ve sampled something called mate, if you didn’t do it in Argentina, I’ll bet you didn’t do it the “right” way (as defined by Argentineans).

According to one survey, mate (pronounced “MAH-teh”—and not to be confused with the Spanish word maté, which means “I killed”) is regularly consumed by some 92% of Argentineans—and by similarly large numbers of people in Uruguay, Paraguay, and Brazil. Superficially it appears to be a kind of tea, but appearances are deceiving. The true story is much more complex.

For starters, there’s the nomenclature. The dried leaves that are brewed to make mate are known as yerba mate—the word yerba meaning “herb.” This is, however, a misnomer: the leaves come from an evergreen tree in the holly family, Ilex paraguariensis. The word mate itself comes from the Quechua word matí, which refers to a certain type of gourd (Lagenaria vulgaris) which, when dried and hollowed, is used as the serving vessel for the beverage. So depending on context, mate can mean the leaves, the container, or the infusion of the leaves in water. The latter sense appears to be the most common—and is thus at odds with the typical North American usage of “yerba mate” to refer to that infusion.

Details, Details, Details

Yerba mate plants must be carefully cultivated and their leaves harvested at just the right time. The leaves are briefly roasted to preserve their color and prevent spoilage, then dried thoroughly, coarsely ground, and left to age for nine months. Finally, they are crushed and packaged. One supermarket we visited in Patagonia had an entire aisle of mate—dozens of varieties, textures, blends, and package sizes. But even the highest-quality brands were inexpensive: a few dollars or so for a kilogram.

The gourds come in every conceivable shape, size, and color, usually with a three-legged metal base (to prevent tipping, since the bottom is convex), and often with a metal ring around the hole in the top, to reduce wear. Although actual gourds are most common, we also saw mate pots made out of clay, ceramic, metal, and even cows’ hooves and horns. Each gourd also requires a special accessory called a bombilla—basically a metal straw with a strainer at the bottom. Instead of filtering out the tiny leaf fragments when the beverage is brewed, drinkers use the bombilla to filter it as they sip.

To prepare mate, one must begin with a properly “cured” gourd—one that has been soaked or cleaned in one of several ways to remove the residual oils that could adversely affect the flavor. The gourd is then filled about two-thirds full of yerba mate leaves, shaken, and tipped at an angle. A small amount of hot water is poured into the empty side, and after a couple of minutes, the bombilla is inserted and a larger quantity of hot water added. Each of the numerous books and websites I read that described mate preparation had different instructions for the precise method of creating an ideal mate—and in fact, many people prefer to leave this immensely important and challenging task to a cebador, a local expert in mate preparation. Every source I consulted, however, was in agreement that unlike tea, mate must never be made with boiling water.

Mate has the somewhat bitter taste of tannins, much like tea. Because of the ratio of leaves to water, it is a very strong flavor. Some of my companions likened it to “grass,” “hay,” or “alfalfa.” I believe these descriptions were intended to be uncomplimentary. I felt about the taste the way I felt about coffee the first time: kind of bitter, not immediately appealing, but I’ll bet it could grow on me.

Drink Me

Mate is normally shared among several people. I read in two different books that each person customarily takes a sip or two from the bombilla, passes the mate to the next person, and the cycle continues. When the liquid gets low, more hot water is added. However, a reader from Buenos Aires informed me that the custom as he knows it is for each person to finish the amount of water in the gourd and pass it back to the cebador, who then refills it and passes it to the next person.

In any case, because such a large quantity of leaves is used, it takes a long time for a single dose of mate to lose its flavor. The people we observed drinking mate appeared to be unconcerned about sharing germs. Apparently in some situations individual, disposable bombillas are used—but more for convenience than hygiene. Our guide did tell us, though, that according to legend when companions share a mate, they will also share their dreams. I did not check to see what other members of our group dreamed about the night after we shared our first mate, but it makes a nice story in any case.

Purists drink their mate hot and unsweetened—just the way I like my coffee. But I read repeatedly that some segments of the population, such as women, children, and city dwellers (if you can believe such categories) prefer their mate cold and/or sweetened with sugar—and sometimes even prepared with milk. We observed locals drinking mate at all hours—in fact, pretty much constantly throughout the day—except with meals. The quantity typically ingested in a day puts my considerable coffee consumption to shame. In order to be assured of a ready supply of raw materials, some people carry around leather cases large enough to hold a gourd, a thermos full of hot water, and a large bag of yerba mate.

Mate is a mild stimulant—when brewed, it has about half as much caffeine as coffee. Some people believe that unlike coffee, mate’s stimulant effect disappears very quickly when you stop drinking, so it can be consumed safely at bedtime. Mate supposedly functions as a digestive aid, which seems reasonable enough; it’s also used as a laxative. Other health claims abound: mate is said to curb the appetite, boost immunity, combat the effects of aging, and even return gray hair to its original shade—among many other benefits. How many of these effects are genuine, I can’t say. But I suspect its health benefits handily beat those of coffee.

Argentineans who drink mate all day long take it very seriously—they must have just the right brand, prepared just the right way in just the right gourd. And of course, “just right” differs enormously from person to person. In this respect, the mate phenomenon is very much like the culture of coffee snobs in the United States. I did bring home my own mate kit, and in fact my gourd is pictured above. (Needless to say, all the supplies to make your own mate are readily available online.) Whether I ever trade my coffee fanaticism for mate remains to be seen, but if I suddenly seem younger and healthier, you’ll know why.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on January 29, 2005.

Adventures with GPS and hiking boots

Hark back with me to a time, long ago, when human beings outnumbered GPS receivers. I know, it’s weird to think about, right? But at this moment I have a GPS receiver built into my smartphone and another built into my smartwatch, and at a rough tally, the total number of such devices in my house right now is eight. Once a specialized, expensive gadget for outdoorsy types with plenty of disposable income, they’re now so common we barely think about them. Every time you ask your car or your phone for directions, you just assume that its GPS circuitry will know where you are and be able to tell you how to get exactly where you want to go.

But back in 2003, when even someone with as much of an interest in gadgets as me couldn’t come up with a good reason to buy a GPS receiver, I was tickled to read an article about a new activity just for those relatively few people with the right hardware. Combining recreation, exercise, high-tech gizmos, and a bit of detective work, geocaching was, at the time, the latest geek rage.

I’m In It for the Cache

Geocaching became possible in 2000, when the U.S. government eliminated a policy called Selective Availability that artificially reduced the accuracy of GPS measurements by non-military folk to a radius of about 100 meters. Once much more precision was possible for civilians, interesting new applications emerged, one of which was a modern version of a treasure hunt. The idea behind geocaching is extremely simple: hide some stuff (the cache), take note of its coordinates using your GPS receiver, publish those coordinates on the web, and invite other people to come find it (using their own GPS equipment as a guide). Nowadays it’s even simpler, as you can just download a smartphone app that’ll display details about all nearby caches on an interactive map.

The cache is usually a watertight container holding a logbook (for finders to record their names and when they located it) and any other random trinkets the owner wishes to include. Usually a cache contains nothing of tangible value; the reward is in the discovery itself, though you might get a small souvenir for your efforts. Finders often leave a memento of their own for the next geocacher who comes upon that site; in more advanced versions of the sport, a cache might contain clues that lead to yet another cache, or an object that’s intended to be relocated to the next cache the person discovers.

Hide and Seek

If your smartphone or any other GPS receiver can indicate your exact position, it may seem as though there’s not much sport—just walk to those coordinates, pick up the box, and you’re done, right? But it’s quite a bit more involved than that. For one thing, GPS receivers still have some margin of error—you may need to search an area with a radius of up to 10 meters. For another, geocaching coordinates generally do not include altitude. A cache could be hidden on the side of a mountain, underwater, in a tree, under a rock, or somewhere inside a public building, all of which would make for a very interesting search. More importantly, knowing where something is doesn’t imply you know how to get to it; the most creative and challenging cache locations are those that require considerable planning, skill, and physical effort to reach.

Geocaching went from a clever idea to an international craze within just a few years. Now, although the newness and exclusivity have worn off, there are approximately eleventy bazillion caches hidden around the world, including dozens within walking distance of my house. There are caches I’ve walked by for years, and would never have known about were it not for the fact that they show up in an app on my phone. And that’s what I find so nifty about geocaching: it’s a way to discover another dimension of your own neighborhood, as you find treasures hidden (almost) in plain sight.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on September 13, 2003, and again in a slightly revised form on January 11, 2005.

Image credit: Pixabay