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Dynamic range is the ability of the sensor to capture a certain range of light and dark, or brightness values. Think of it as the number of keys on the piano the “hand” of the sensor can cover. While the sensor may offer an octave’s worth of tones, this octave can be moved all around the keyboard. If the light is low the sensor can adjust through the use of high ISO and slower shutter speeds and wider apertures. If that range of notes is bright then the sensor can be adjusted to handle exposure with narrower apertures, faster shutter speeds and lower ISO settings. Though there is a wide range of adjustment the sensor and settings can be made to handle there is always a certain range of light that it can record—that’s the dynamic range of the sensor. An important part of mastering exposure is understanding this and seeing light, and especially contrast, the way the sensor sees it.

All Photos © 2008, George Schaub, All Rights Reserved

When making exposures try to exploit and record the full range of brightness values in the scene. This will give you more creative leeway later when you make prints or work on the image in software. The exposure of this fall scene gets into every nook and cranny of detail, even in the dark recesses of the bark. But there are some areas it cannot properly exposure, such as the dark shadows. But these shadows help define form as do some of the brighter highlights.

There is a software technique for combining exposures to get the most from a scene with high contrast values. This involves bracketing exposures, and it is something we will cover in detail in our Tips section. As a preview, here are two shots that have been over and underexposed, and then combined later for the final fuller range image. For most of your shots, however, that extent of exposure work is usually not practical, or even worth the trouble.

Our eyes adapt to changes in brightness because our pupils are constantly opening and closing as we look around, and the signals to our brain are integrated as we look from, say, the deep hollows of a canyon to the bright horizon. The “eye” of the camera, the pupil in the lens, is fixed at 1 EV, so
when we make a picture it is as if we have locked onto a specific brightness, and all other values have to follow suit.

So if we are making a picture of a deep canyon with bright snow surrounding it, making an exposure only for the deep canyon (the shadows) will result in the bright, snowy field recording too brightly, or becoming highly overexposed. In fact, it will be so bright that it will be “burned up” or lose detail. If we lock the opening in our eye (or camera lens) on the brightness of the snowy field we certainly won’t see any details in the dark canyon.

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