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Tuesday, January 26, 2010

Perfectly Wrong Exposures—03/08/10

DPMag Published in Tip Of The Week
Perfectly Wrong Exposures—03/08/10

This Article Features Photo Zoom

Automatic exposure and automatic flash metering sure do make it easy to make correct exposures that help with great pictures. But sometimes even the most accurate in-camera systems make metering mistakes. Even if they aren’t truly mistakes, sometimes purposely creating an over- or underexposure can actually create better photos. Here are three instances in which the wrong exposure can be so right.

For smoother skin, overexpose dramatically. Overexposing, with flash or even ambient lighting, can create high key effects that tend to eliminate skin texture and hide blemishes, wrinkles, shadows and lines. It hides all the things that tend to be unflattering in photos of faces. How should you get it wrong? With ambient light, simply adjust your exposure compensation to anywhere from one to two stops overexposed. With strobe lighting, set your flash on manual, take your meter reading (or simply look at the LCD) and adjust the combination of flash power and aperture until it looks way too bright. Even if you prefer working with automatic flash exposures, you can adjust the power to be a stop too strong thanks to flash exposure compensation.

To optimize your RAW files, overexpose subtly. When shooting RAW files, subtle overexposure (compared to normal or especially underexposed images) tends to make for more detail-rich files that can be adjusted in postprocessing to maximize detail across the dynamic range. That means you can create finished images with more key detail in both highlights and shadows. This is where the ETTR, or “expose to the right” approach, originated. Working with this in mind, check your exposure on the in-camera histogram, and be sure to keep the exposure peaks well toward the right, corresponding to bright, edge of the frame.

To deal with extremes, think like your meter. If you’re faced with a scene that’s predominantly comprised of very dark or very light tones, the camera’s indicated meter reading is often wrong. That means the wrong exposure will in fact be right, so you should manually adjust the exposure or set exposure compensation to compensate. For example, you should set the camera to overexpose a bright scene (such as a snowman on a ski run lit by bright sun) by at least a stop in order to render the scene appropriately in the finished image.

Why overexpose? Because in auto exposure mode, the camera can be fooled into believing all that bright white in the high-key scene should in fact be rendered as middle gray. That would be a disaster for your bright snowy scene, making it dramatically underexposed and gray—unless, of course, you’ve set the compensation to overexpose. The reverse is also true: When photographing a person in dark clothes against a dark background, your camera’s TTL meter is bound to be fooled and overexpose the scene. To compensate for the low-key scene, set the camera to underexpose—and you’ll get an image that’s right on.
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