High Dynamic Range Imaging
I’ve been seeing more and more interest in high dynamic range images online and in the workshops I teach. Judging by some of the books I’ve checked out, you might think it requires a degree in physics or at least rocket science to create this type of image. Like many things digital though, it doesn’t have to be difficult and it can be a great new way to express yourself.
Cameras, both digital and film, can’t record all of the information we can see with our eyes. While you can automatically adjust what you’re viewing to see details in shadows and highlights at the same time, we often have to make exposure decisions based on what areas of the image contain the most important information, and risk losing highlight or shadow detail as a result.
With high dynamic range (HDR) imaging, you can get around this shortcoming in equipment and go beyond what our eyes see to record something special.
Let’s take a look at how easy this can actually be in practice. To start with, you’ll obviously want a scene with a wide dynamic range. A tripod will make the processing effort much easier, and a camera that lets you control exposure is required.
I shot this series of three images at Joshua Tree National Park at dawn. Using exposure bracketing, I recorded one shot at the suggested exposure to record the midrange detail, another at two stops under to get the most detail possible from the sky, and a final image at two stops over to open up the shadow detail. Photoshop CS2 and CS3 includes a “Merge to HDR” function (found under the File > Automate menu). But I prefer to use Photomatix because it does a better job and gives me more creative options in processing the images.
When you work in HDR, you’re working with a 32-bit file. In other words, you have plenty of information to work with. But Photoshop requires images to be in 8- or 16-bit mode to do any processing work, and many printers can only deal with an 8-bit image.
FIGURE 1
FIGURE 2
FIGURE 3
In Photomatix, I open the three images (Figures 1, 2, and 3) and tell the program to merge them together. The result is not what you’d expect as the preview looks like a dark mess. But, now the magic starts. When I go into the Tone mapping dialog I’m can control how this extra detail is going to be displayed.
FIGURE 4
You can get as accurate or as creative as you like at this point. For this particular image, I liked the surreal look generated by enhancing the lighting, saturation, and contrast (Figure 4).
For final output, I sent this to my Designjet Z3100 using HP Instant Dry Satin photo paper. With the Gloss Enhancer on this paper I get excellent results with great vibrant color – just like my vision for this image when I processed it.
