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Tuesday, November 8, 2011

Auto HDR, Quicker, Faster And Better?

New DSLRs with Auto HDR features can create high dynamic range images in just seconds, but are the results worth the convenience?

This Article Features Photo Zoom
At the lowest Auto HDR settings, which generally capture a 2-stop exposure range, an HDR JPEG of a high-contrast scene always will beat out a normally exposed JPEG. But at that setting, shadow and highlight details may be similar or only slightly improved over a TIFF or JPEG file created manually in postprocessing from a RAW file. That's because most RAW files contain a stop or slightly more of useful shadow and highlight details that can be culled by RAW conversion software, more so in the shadow direction than in highlights. A number of software programs and utilities have been designed to take advantage of that fact, automatically optimizing the exposure range of a RAW file into a pseudo-HDR image. But if the range of a scene is above the 8 to 10 stops captured by the imaging sensor, you can't extract detail that isn't there, and only merged multiple exposures will do the trick.

Since each manufacturer uses proprietary image-processing algorithms and its own processing engine to create HDR JPEGs from multiple exposures, the image quality results may vary from camera to camera and from scene to scene. In addition, the most realistic results are always created when there's little or no subject movement in the scene during the bracketed exposure sequence, or when the photographer grips the camera firmly or sets a higher shutter speed to minimize shake when shooting without a tripod.

HDR 3-Stop Range

HDR 5-Stop Range

Bottom Line
The Auto HDR mode isn't perfect, but it's certainly the fastest way to create a near-perfect JPEG of a typical high-contrast scene, as well as a true HDR image of a very high-contrast scene. For now, controls are limited, and in-camera processing prevents you from shooting for several seconds while images are being merged. But you'd be hard-pressed to top the results or save more time by processing a single RAW file, and this feature is bound to be a big hit for photographers who don't mind printing or sharing high-quality JPEG images.

Michael J. McNamara
has decades of experience in imaging technology. See more of his reports on trends and technologies on his McNamara Report website at www.mcnamarareport.com.

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