Expanding Photography’s Tonal Range

HDR photography lets you capture images of great brightness range that are closer to the reality you see

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Left: Before, Right: After

One of the great challenges of photography is capturing a scene that we see well, but the camera doesn’t. Neither film nor digital sensors are capable of recording all of the tones in a scene that has a great range of brightness, such as rock formations against a sunset. Usually you get something of a silhouette, yet you know that you saw detail in both the sky and the ground.

The range of tones in a photograph is its dynamic range. A scene with a large variance in these tones from dark to light will have a high dynamic range, a range that isn’t typically recorded by a camera.

Consider a scene with light striking a cliff directly, but with trees and rocks in the foreground receiving only light from a darkening sky. Such brightness range is especially beyond popular films such as Kodak Kodachrome or Fujichrome Velvia, so typically, the photographer would expose for the bright light and let the rest go.

The result is a richly colored cliff from the late sun, but pitch-black trees and rocks, which could be used as a dark frame to the cliff, but not much more. Such images could be dramatic shots and beautiful interpretations of a scene, but they weren’t particularly accurate in depicting what nature really looked like.

Enter the power of the computer and digital photography. Now we can deal with extreme brightness range and start reconsidering what’s possible with our photography. There are several things you can do to help deal with extreme contrast range, including double-processing RAW and shooting two exposures of the same scene to be combined in Photoshop.

First, let’s look at HDR (high density range) photography. A simplified explanation of this is that you take multiple photographs of a scene at a range of exposures and then bring those exposures into a special computer program that combines the exposures into one image that shows the whole range of the scene’s tonality. I first tried this with the HDR feature in Photoshop, and I was unimpressed. It seemed like a great idea, but the implementation didn’t work that well for the photographs that I tried. It seemed too much like a “work in progress.”

I saw a number of photographers bravely start working this way with HDR photography, and they did get images with a lot of range in tones. But the photos looked a bit flat to me and didn’t have the life I expected in good nature photography.

Some photographers started exploring this technology early on. I liked some of the photos, but others looked too “gee-whizzy” for me—the effect called too much attention to itself.

Then this past winter, George Lepp sent me several new photos. He had mastered the technology. The photos were terrific, and I now saw a range of possibilities. The software George used was called Photomatix from HDRsoft (www.hdrsoft.com). I checked the website and discovered that this software offered exactly the sort of controls in which I was interested, plus it was reasonably priced.

When I installed the program, I went to some photos I took during one of my workshops in Costa Rica. I had bracketed a sunset shot with the possibility of using parts of two exposures in one image. The shot wasn’t too exciting, but when I tried it in Photomatix, I was excited. I suddenly found I had an image with the tonality of the dark rain forest as well as the bright sunset sky. This was impossible! Yet, it happened, and I knew I had a new tool.

Next, I was in the Mojave Desert outside of Las Vegas, in the Lake Mead Recreation Area and the Red Rock Canyon National Conservation Area. I tried shooting all sorts of scenes by setting my camera to autobracket, with one-stop changes between each shot, using both three- and five-bracket series. I even tried some shots that I never would have attempted before because the contrast range was too great. When I brought these images into the computer and started playing with them in Photomatix, I was thrilled to see amazing things start to happen. Scenes came alive in ways that I had never experienced before.

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What makes Photomatix work so well is that it not only puts the tonalities from multiple shots together into one image, but also offers excellent control over those tones in something called Tone Mapping. You can adjust the strength, color saturation and, very important for my interpretation of the HDR file, light smoothing (this can go from a rather funky look to something totally real). In addition, you can set white and black points, which I consider key to good digital photos.

I can’t say that every “shot” (made of multiple exposures) looked great—Photomatix can only deal with what it gets from the photographer! But I was hooked, and now I’m always looking for HDR types of images in locations where I shoot so I can get photos that actually capture something closer to what we see. I usually do a little added work in Photoshop to give the image more structure by selectively darkening and lightening parts of the photo as done in traditional photography in the darkroom.

If you want to explore the idea of working a scene so that you capture more tonal range than a single shot normally does, you also can try two techniques that I still use and can be quite effective—double-processing RAW and shooting two exposures of the same scene to be combined in Photoshop. Both use Photoshop in the same way to combine two versions of the same scene showing different tonalities (you can do even more than two versions, but I rarely find a need to do that).

The double-processing RAW technique is fairly simple. You process a RAW image with challenging dark and light areas by processing once for the dark areas and a second time for the light areas. You can do this in any RAW-processing program, from Camera Raw to Lightroom.

Often with scenes with extreme tonal ranges, you end up compromising when you try to process it all at once, and neither the dark nor the light areas look their best. By processing each version focused purely on first dark and then light tones (and ignoring what happens to the opposite tones), you can more easily get the best from both tonal ranges.

photoshop screenshot

With the other technique, you have to shoot two photos of the scene (camera on a tripod)—one for the dark areas, one for the light areas—and then process each specifically for those tones. I find this easy to do by using autobracketing and exposure compensation. The brightest photo is good for the light areas—I keep the brightest and darkest exposures and throw out the middle shot. By autobracketing, I avoid having to move anything on the camera (such as shutter speed or ƒ-stop) that can make the camera move slightly between exposures. If the camera moves, it can make it harder to line up these shots in Photoshop.

Either way, you end up with two separate images in Photoshop—one light, one dark. Keep both open and visible on your monitor and then, using the Move tool, press the Shift key, click on the better-looking image and drag it over and onto the other photo. If you get an error message, it means you didn’t drag your cursor far enough onto the other photo. Release the mouse button and then the Shift key. The Shift key means the two photos will align exactly on the edges.

This literally puts two photos in a stack, one on top of the other as layers. If you had two real photos in such a stack, you’d cut holes in the top one to reveal the one underneath. You do exactly the same thing in the computer. You can do this by using a soft eraser brush (easy to do) or a layer mask (better because it gives you more control).

If the top photo is the darker one that favors the light parts of the photo, just go in and remove the darkest areas, which allows the better dark-processed or exposed tonalities to appear. If you use an eraser, you have to use the History palette to back up if you make a mistake.

Try adding a layer mask (found in the Layer menu or click on the little rectangle and circle icon at the bottom of the Layers palette). Paint black with a soft brush over the areas you want to remove. Black blocks whatever is on that layer, revealing what’s underneath. Any techniques (and there are several that require more space than I have here) that put black in specific areas will help combine these images.

Regardless of how you do this, bringing a larger range of tones into a photograph than is possible using traditional techniques gives the nature photographer a powerful tool to create images closer to reality. You gain some great possibilities for your photography that go beyond the limits of what a sensor or film is capable of seeing.