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Tuesday, December 1, 2009

High Dynamic Range Done Naturally

Explore the basics of HDR to get details in shadows, highlights and everywhere in between

This Article Features Photo Zoom

Mountain ridges and fog illuminated by the rising sun, Rocky Mountain National Park, Colorado. A single RAW exposure was all I needed to hold detail in the highlights while exposing for the shadows in this image. TheRAW file was processed with Adobe Camera Raw to hold detail in the highlights and shadows.
Combine Exposures For High Dynamic Range
This is the part that gets a little tricky, and you need to make some key decisions at capture and in postprocessing to develop the files. I see many photographers today bracketing exposures to combine images for tone mapping in popular software programs like Photomatix and FDRTools as a way of handling their HDR images. While tone-mapping images can be fun and at times produce great results, it has been my experience that most images tone-mapped in HDR software take on an illustrative and unnatural look. While this is fine, and I’ll be the first to say that creative choices are up to the individual photographer with no right or wrong way of doing any particular technique, I tend to prefer a more natural result for my nature photography.

The way that I approach this problem is to bracket a set of images in the field. Make sure you have your camera locked down on a tripod, as there can be no shift from image to image for this to work. If your camera offers you the ability to auto-bracket, use it. Once I’ve set my base exposure for the midtones in the scene, I’ll usually bracket five frames at one-stop intervals. This will cover the dynamic range of most images, but on occasion, you may need to bracket a little further in one direction or the other. The important thing here is to check the histogram of each image to make sure that you’ve recorded at least two images with sufficient detail in the shadows and the highlights.

Using The RAW Converter
Once I get my images into the computer, I usually choose two shots, one for shadow detail and another for highlight detail. I open up both images in the Adobe Camera Raw converter and apply specific adjustments for each one, including white balance, recovery, fill, curves, tonal adjustments and saturation.

Mather Gorge, Great Falls National Park, Virginia. Just as the sun began to rise, it momentarily broke through the clouds and illuminated the sky in warm, dramatic light. The exposure difference was more than my graduated filters could handle so I made two exposures, one for shadow detail and one for highlight detail. The two images were combined in Photoshop CS3 using layers and a mask for a seamless blend. Nikon D2X, Nikkor 17-35mm, RAW capture at ISO 200
Once I’ve finished tweaking each image in the RAW converter, I open them up together in Photoshop. The first step in my workflow is to grab the darker shot and Select All, then Copy and Paste that image onto the lighter version. This creates a duplicate layer, and you have the option of blending the two images together. I usually use a Channels selection (blue works great for sunrises and sunsets) and apply a mask to the layer. This requires you to grab the paintbrush and tweak the opacity of certain regions of the mask until the blend is seamless. Another way to do this is to add a mask to the layer and simply use the paintbrush at different opacities to reveal the background (lighter) image below. If you’re working with Adobe Photoshop CS4, you should use the Mask Tool Box to properly feather the blend. For photographers without CS4, you can select the mask and go to Filter > Blur > Gaussian Blur to feather the mask for a more seamless blend.

I know this sounds complicated, and at first it can be a challenge to learn, but once you’ve mastered the art of blending images, you won’t look back. It will allow you to create more realistic HDR images of the natural world.

To see more of Joseph Rossbach’s photography, read his photo blog or learn about upcoming workshops, visit www.josephrossbach.com.


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