Dynamic Range Examples
© Peter K Burian
All Rights Reserved
Whenever we take photos in harsh lighting, areas of the scene that are in shade tend to be dark and murky, without any visible detail. This effect, caused by extremely high contrast, is not a problem in situations where the shadow areas do not contain any subjects of interest. At other times however, it would be very useful to have detail throughout the entire scene.
While electronic flash can be useful in a small room for example, even a powerful flash unit cannot illuminate an entire landscape or the vast interior of a palace. Fortunately, most recent cameras provide a feature that can help to lighten shadow areas for a more pleasing overall effect. It's called Auto Lighting Optimizer (Canon), Gradation Control or Shadow Adjustment (Olympus), Active D-Lighting (Nikon), Expanded D-Range or Shadow Compensation (Pentax) and Dynamic Range Optimizer (Sony).
Notes on Dynamic Range Examples (at right): This high contrast situation (bright glass, dark surroundings) produced an image that was too dark overall, when exposing for the windows. Setting the shadow lightening feature to Automatic produced some improvement while the highest level (with a Sony DSLR) provided a dramatic increase in shadow detail.
Imagine a thick forest on a sunny day. Because of the many trees, most of the scene is very dark, but small areas are intensely bright because they're illuminated by shafts of sunlight. This is definitely a high contrast situation. After you take a photo, you'll find that it exhibits one of two distinct problems.
#2, Lost Shadow Detail: But let's say that your camera's metering system considered primarily the bright areas, or that you had set minus exposure compensation to prevent overexposure of the trees and foliage. In this case, the bright areas of the photo will be nicely exposed but the darker areas will be much too dark. Take the photo again, but this time activate the shadow lightening feature for better results.
The technology discussed earlier differs from camera to camera, but Active D-Lighting, Dynamic Range Optimizer (DRO), etc., will activate extra processing to lighten shadow areas and some mid-tones. A few systems can also tone down very bright highlight areas slightly. With the better cameras, the user can set the desired level for shadow lightening, either Automatic or Low or High.
Sony Alpha cameras offer the highest intensity levels of any that I have tested. By Level 5 for DRO, you get very obvious shadow lightening. (A lower level may be preferable for a more natural-looking photo.)
Depending on the camera you use, this feature may be on by default at the Auto level or you may need to activate it. As the photos used for illustration indicate, Auto typically provides moderate shadow lightening. In very harsh light where shadow areas are very dark however, you may need to set a much higher level.
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