Pro Techniques

In the early days of digital imaging, we were promised much. Suppliers, manufacturers, photo writers, and early-adopter photographers talked about how digital would allow us do more with photographs. We'd be able to see them instantly, send them quickly, and, most important to the serious-minded among us, control them creatively. Digital cameras and the digital process would allow us to do things we could never do before--like change the ISO in mid-shoot. We heard that we'd be able to capture images that were once impossible.

Ferrell created this HDR image of the Washington National Cathedral in Washington, DC, from seven images at 1 EV spacing. The perspective is due to his use of a 10.5mm fisheye lens. "I needed seven images to capture the details of the towers in the bright sun and the ceiling of the shaded gazebo." All Photos © 2008, Ferrell McCollough, All Rights Reserved

At first many were skeptical. Technology had always promised a lot and delivered mostly advertising slogans. Computers were going to make our workload easier, our workweek shorter. Electronic communication would create the paperless office. How'd those work out for you?

But digital imaging delivered. The promises were kept, and the end is nowhere in sight.

Ferrell captured this image of car taillights in five photographs at 1 EV spacing. "Each exposure records the action in a different position," he says, "so this final image required some post-processing cloning to correct ghosting."

Digital isn't responsible for the development of High Dynamic Range (HDR) photography, but it makes it easily accessible. In an HDR photograph we can finally see reproduced on paper and displayed on a monitor the wide range of tones that our eyes can perceive but no film or sensor can capture in a single image.

HDR photography involves taking a series of exposures of the same scene, each at a different EV setting, and using a software program to combine the images. With your camera on a tripod, you take a bracket of three, four, or more exposures, ranging from under- to overexposure; in that series you'll capture all the shadows, highlights, and mid tones of the scene. The software--and the decisions you make about how you're going to use it--will basically do the rest. The result is an image that combines the best of our individual takes, complete with color in the highlights and details in the shadows. What you need is a camera capable of exposure compensation control (auto-bracketing is a plus), a tripod, a computer, and the software.

The software performs essentially two functions: merging, which creates from your exposures a 32-bit file that represents in one image the full dynamic range of the scene; and tone mapping, which converts the file back to a range that's able to be viewed on screen and on paper.

Four images were taken using a handheld flash with a different color gel for each flash exposure.

I talked recently with Ferrell McCollough, a professional photographer who's written the Complete Guide to High Dynamic Range Digital Photography. I didn't want to find out the details of how the process works--that's in his book, and in the books of others, of course; I wanted to know why he became fascinated with HDR.

"I saw HDR photos for the first time at the Flickr website," Ferrell says, "and I was blown away by the detail in the shadows. I didn't know what it was yet, but the wow factor just grabbed me."

Eventually he picked up enough information to start doing it. "It opened up the possibilities. I used to never take a camera out of my camera bag at noon; in fact, I'd avoid any shooting after 9am and before 5pm. Now I take the camera out at any time. HDR has expanded the time when I can shoot and get good images."