How Digital Photography Works

Every time you go to a different

place it’s lit differently.

Annie Leibovitz

ALLphotography is about light. Photos may be of important or trivial subjects, in color, or black and white.

A picture may be as candid as the next minute’s news or a painstaking pose, a slice of reality or a helping of the

abstract. It can be still or moving, invoking weighty subjects or the flightiest of fancies. But whatever else pho-

tographs are, they are about light.

They are about what light does when it flickers off a river, when it exposes the wrinkles and buried veins of age,

how it transforms a sky, or how it creates depth and curves and textures you can feel with your eyes. Photos are

even about light when there is none, or at least very little, when a photo’s subject is buried in shadows and the

slightest feature forcing itself out of the depths of blackness becomes enormously important.

Light is the tool and the curse of photographers. In a studio, hours may be spent adjusting lighting and shooting test

shots to create the exact right balance of highlights and shadows. In candid photographs, landscapes, and action

shots, the state of lighting is more often an accident, forcing the photographer to make quick, on-the-fly adjustments

and guesses about what light the camera will capture at...thisvery moment. If the photographer is successful, and

lucky, he captures a moment of light and dark and color that will never exist again except in the bits and pixels

where that moment now resides, possibly forever.

A paparazzo snapping a photo of Brad and Angelina is much like a batter hitting a home run. The batter has to cal-

culate the changing speed, trajectory, and spin of a fast ball and its diminishing distance from him, and translate

that into the timing, speed, and angle of his swing. The batter analogy would have held up a lot better 50 years ago

before automatic features were built into a camera, making off-the-cuff shots less of a grab bag.

Today’s digital photographers have even more wonderfully computerized tools to help decide when the light is just

right for the nabbing. Plus, they can turn fluorescent lighting into daylight, and daylight into candlelight. They can

change the sensitivity of their “film” in the middle of shooting or turn color into black and white. The digital photog-

rapher gets to play with light as if he made the rules that light beams must follow. And that’s because he does make

the rules. Here’s how it starts, with the fraction of a second called “exposure.”

CHAPTER 5 HOW DIGITAL EXPOSURE SIFTS, MEASURES, AND SLICES LIGHT 63