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?

Text And Photography By Michael J. McNamara

Labels: How-To, Camera Technique

This Article Features Photo Zoom

Quicker, faster and better?

In the last few years, high dynamic range (HDR) photography has become incredibly popular, propelled in part by the capabilities of both digital cameras and HDR-enabled imaging programs. As a group, outdoor photographers have been the biggest beneficiaries of the HDR process, as it enables us to tackle high-contrast scenes in nature and produce HDR images that more closely match our visual experience. Creating an HDR image isn't new to digital, but with film it was a tedious process that required skill, an expensive darkroom and lots of trial and error. With digital photography, you can create an HDR image in the computer much easier and with better results. DSLRs can shoot a burst of bracketed exposures, and using a variety of HDR-enabled software programs, you can create an HDR image by combining elements from each exposure.

Camera designers apparently didn't think this was easy enough, which explains why there are now Auto HDR modes in several new DSLRs from Nikon, Pentax and Sony, and we expect the trend to continue. At the push of the shutter button, these cameras shoot a quick burst of exposures and then use their powerful image-processing engines to merge them into an HDR JPEG image. As a bonus, several Pentax and Sony models can correct minor camera movements that occur between frames in the burst, allowing you to create HDR images without a tripod!

The Auto HDR function cuts out the postprocessing time and effort, but many HDR purists and photographers who prefer to have the option of controlling their images more down the road cringe when they learn that all current Auto HDR modes create an HDR JPEG file (8-bit) from the exposure sequence and not RAW or TIFF files (16-bit). On top of that, Auto HDR modes in the Pentax and Nikon cameras discard the entire exposure sequence used in the process, so there are no "redos" or adjustments possible after the creation of the HDR JPEG. The Sony models store two images—a normal exposure JPEG and an HDR JPEG—so you can quickly compare results. If you don't like what you see on the camera's LCD monitor, you'll be forced to change modes or HDR settings and shoot again.


Normal Exposure	HDR 2-Stop Range	HDR 5-Stop Range
These images were taken with a Sony SLT-A35 DSLR in Auto HDR mode. The camera allows you to adjust the HDR effect by increasing the difference between three exposures—Under, Normal and Over. The camera combines the exposures, increasing details in shadows and highlights, and lowering overall contrast. For most scenes, a 2- or 3-stop-range setting is the most pleasing.

The only Auto HDR controls that exist allow you to select the exposure range between the images in the sequence from a 2-stop range to about 6 stops, as well as choose the resolution and quality of the final HDR JPEG file. You also can select full Auto HDR, which tells the Sony models to select an appropriate exposure range based on scene contrast, or in the case of the Pentax models, set the camera to a 2-stop range: -1 stop, Normal and +1 stop.

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