An image taken with a Lytro camera is not really an image, but a machine capable of producing many possible renditions.
The Lytro Light Field Camera
Let's think about photography as people live it. A posed family picture might be taken once, then again, and again until the right combination of open eyes, smiles, and light and shadow produce an acceptable portrait. An action, performance, or sports shot that could speed by too fast for human judgement partakes of a surrogate: the high-speed motor drive capable of taking many shots per second, from which the photographer later chooses the most retrospectively opportune option. You don't have to be a professional to recognize a "missed shot" taken near to but not right at the opportune moment. Photography freezes moments in time, so capturing the right moment in the right way is important.
Getting an exposure precisely right is part of the craft of photography, but also part of its frustration. Someone's eyes always seem closed, or the lighting changes, or an accidental jitter of the photographer's hand shifts the framing or focus inadvertently. Corrections can sometimes be made after the fact in the (digital) darkroom, but even an amateur photographer knows that some exposures are always doomed -- a blurry image can never be recovered with chemical or software exposure correction. Lytro, a Silicon Valley startup co-founded by a Stanford computer science PhD named Ren Ng, has been working for the last six years to prove otherwise -- and to change the very idea of what a photograph is in the process.
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Photography didn't used to be so easy. Before the 1920s, most high-quality photographs were taken with view cameras: large, bulky devices with bellows necessitating tripods, lights, and long exposures to expose large film plates. These were the tools of Brassaï and Walker Evans and Ansel Adams, devices that offered superb resolution and detail thanks to their larger film plates, which were typically reproduced with low- or no magnification during printmaking.
Like every important artistic material, the view camera remains a viable and appealing medium for photographers. But using one in the late 20th century (as did Stephen Shore and Sally Mann, to name but two famous examples) requires making a deliberate aesthetic choice. By contrast, in the early 1900s, "still camera" just meant "view camera." It's the type of shift everyone should be familiar with today. Just think of the different connotations of "computer" in 1962, 1982, and 2012.
Still, entirely new photographic apparatuses are relatively rare. The transition away from the view camera era began between the two world wars, when manufacturers devised apparatuses that adapted cinema film for use in still photography. These were the first 35mm cameras, the most famous and influential of which was the Leica.
Almost all of today's cameras, analog or digital, owe something to the 35mm film format and the devices that exposed that film, so it's easy to overlook the formal properties that characterized the Leica when it was new. Most of all: size and portability. The Leica could be held and pocketed, and its film could be exposed quickly through short lenses that let through enough light to produce appealing images wide-open or stopped-down. It wasn't the first camera to open photography to snapshooting (the Kodak Brownie deserves that laurel), but it was the first serious, popular, professional example of photographic process that we know today.
The photographer Henri Cartier-Bresson is probably the most famous 35mm photographer. His work helped established reportage, street, and candid photography as a viable artistic and practical affair. His small Leica rangefinder could be easily carried throughout the streets of Paris, New York, Madrid, or Budapest, looking for fleeting moments that could be captured with precise timing, framing, and focus before they vanished forever. The camera was as much a partner in this affair as was the photographer: Cartier-Bresson could zone-focus wide-angle lenses stopped down to medium- to small-apertures, such that he didn't have to look, frame, and focus a scene before capturing it. Shooting from the hip became as common as shooting from the eye for street photographers looking to remove themselves from a scene so as not to disturb it.
Cartier-Bresson called this window the "decisive moment." This search for the fundamental instant in a particular time and place has become synonymous with candid and street photography. In a 1957 interview with the Washington Post, Cartier-Bresson offered a compact definition of the concept:
Photography is not like painting. There is a creative fraction of a second when you are taking a picture. Your eye must see a composition or an expression that life itself offers you, and you must know with intuition when to click the camera.
That is the moment the photographer is creative. Oop! The Moment! Once you miss it, it is gone forever.
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The early days of digital photography intensified our attention to the decisive moment, as cheaper digital cameras exhibited shutter lag -- a delay between the time the photographer actuates the exposure and the recording of an image. But the decisive moment's prominence has also hidden other important aspects of photographic craft. A photograph can be made at the right time, but with the wrong exposure. Or it can be correctly exposed, but with a shutter speed inappropriate for capturing its action, or an aperture that produces too much or not enough depth of field. A picture can be mis-framed so that a key subject is in an undesirable location. But even so, darkroom and digital tools have offered solutions to most of these problems. An oddly framed negative could be cropped before or after enlargement, or with a single click in Photoshop. An over- or under-exposed image might still be restored in the darkroom or in software postprocessing. With digital photography, white balance and color balance can be easily corrected. A blurry photo can never be made sharp, but it might offer a desirable aesthetic outcome anyway -- a decisive moment found unexpectedly.