Tuesday, February 12, 2013
The Universal Exposure Strategy
How to harness the power within your camera and your eye to get perfect exposures for every kind of lighting situation
Menacing gray clouds filled the sky when I arrived before dawn on the crest of Black Face in the San Juan Mountains near Telluride, Colorado. I had wagered a good night's sleep on this sunrise, but my decision to get up at 2 a.m. and hike two and a half hours in the dark looked like a gamble I had lost. Minutes later, however, the clouds to the east began to tear apart, revealing ragged holes rim-lit with golden light from the rising sun. The scene was spectacular, but with both backlit clouds and deeply shadowed, forested valleys in the frame, the contrast was high.
When I'm rushed, and nothing is moving within the frame (the big caveat), I often resort to the Universal Exposure Strategy. I set the camera to give me a five-frame bracket set with a one-stop bracket interval. With that strategy, I can come away from the shoot confident that I have the data to choose, after the fact, whichever basic exposure strategy will give me the best result.
Let's investigate the four basic exposure strategies more deeply.
1 PhD No, you don't need a doctorate. PhD stands for Push here, Dummy. If you're shooting a midtone subject in soft, even lighting, your camera will give you the right exposure time after time. The most common PhD situation is an intimate landscape of wildflowers on an overcast day. With no sky in the frame, the meter reads primarily off the green foliage, which is a classic midtone subject. The entire sky is the light source. Such a broad source gives you low-contrast lighting. You can forget about exposure and concentrate on composition.
2 Limiting Factor This is the best exposure strategy to use in slightly higher contrast situations. The limiting factor is the highlights: Don't blow them out! The simplest procedure is to shoot a test frame at the exposure recommended by the camera's meter, then check the histogram.
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