Mastering the HDR Landscape
Landscape photographers often find themselves in challenging light. If you're at all experienced with shooting landscapes, then you know that the best light happens in the hour or so right around sunrise and sunset. The so-called "golden hour" is when we get nice, warm light and excellent opportunities for side-lighting to bring out the texture in terrain. If you shoot right around sunrise and sunset, though, you'll also get the problem of too much dynamic range.
Dynamic range is the term photographers use to describe the ability of film or a digital sensor to capture brightness values, while still preserving detail. When the dynamic range of a scene exceeds that of your sensor, you end up with either blocked (black) shadows, clipped (white) highlights, or both. Depending on your scene, this can either add dramatic contrast or just look plain awful.
For nearly a century, photographers have struggled with different ways of dealing with high-contrast scenes. Ansel Adams devised the Zone System to help him understand the tonal relationships of his subjects when shooting with black & white film. Adams also used darkroom techniques like dodging and burning to help recover shadow and highlight details in the final print. Graduated neutral-density filters (ND-Grads) are another tool that help us deal with high-contrast scenes. These filters compress tones in the image by darkening highlights while we expose for shadow detail. The trouble with ND-Grads is that they are a bit tricky to use in the field, and only work well for subjects with well-defined horizons.
This image of the Maroon Bells, near Aspen, CO, would be nearly impossible to produce with traditional photographic techniques.
21st Century Techniques: HDR
When Adobe released Photoshop CS2, they included the first mainstream application of high-dynamic-range (HDR) imaging. With HDR, a photographer can combine a bracketed series of exposures into a 32-bit-per-channel image. This 32-bit image contains more tones and colors than what any monitor or printer can display, so photographers then must "tone-map" the 32-bit image back into a standard 16- or 8-bit-per-channel color space. Unfortunately, early tone-mapping tools were cumbersome to use, and often delivered psychedelic and bizarre results. Since CS2, other products have come out that make producing "realistic" HDR images far easier for the average photographer.
HDR Basics & Field Techniques
When photographing HDR landscapes, you need to know some basic ground rules. First, you have to ask yourself whether the scene is a good candidate for HDR. If there are lots of moving objects in the scene, it's probably better to go with a grad filter, and try your best with a single exposure. Keep in mind that you will need to produce between 5-9 images for a good HDR merge. These shots cannot be made simultaneously, so you'll want to try to use your camera's high-speed advance if possible. Lastly, you need to "lock" everything in your exposure series except for shutter speed. Use a tripod, dial in a fixed white balance setting, and set your camera to auto bracket in Aperture-Priority mode for best results.
How many shots should you take? The traditional HDR sequence has five shots: -2, -1, 0, +1, +2EV. Ninety-five percent of the time, this is all you'll need, especially if you are shooting in RAW and outputting 16-bit TIFF files for HDR merging. There are some scenes, however, where you'll want to add more frames. Typically, if you are shooting directly into the sun, you'll want a 9-shot series. That will give you your metered exposure +/-4EV of bracketing. You can also combine exposure compensation with auto exposure bracketing on some cameras. This will allow you to bias the exposure towards the highlights or the shadows as needed.
Once you've made your shots, then you need to apply the same approach of "locking" everything to your post-processing. I output 16-bit TIFF files from my RAW converter using identical settings for color, contrast, and white balance. If I change something in one file, I paste the same settings into the other files in the sequence. I also turn off all image sharpening so that I don't get any weird artifacts when I'm tone-mapping my images. I'll sharpen as a final step, after I blend the images together.
Tone-mapping is what makes or breaks your HDR image. For landscapes, the trick is to produce an image that is as natural-looking as possible. This is very easy if you use Nik Software's HDR Efex Pro software. Not only is the default setting very realistic, but this software allows you to make localized adjustments to brightness, color, and contrast right on your HDR image, without the need for another editor. To make it even easier, you can download from my website a set of 14 custom tone-mapping presets that I developed with the help of master photographer Tony Sweet, for use with HDR Efex Pro. These custom presets work on just about any image, and give you a very good starting point from which to create masterful fine-art HDR images.
If you use Nik's HDR Efex Pro, you'll be amazed at how easy it is to create natural HDR landscapes. Once you've finished with the tone-mapping steps, all that's left is sharpening and special effects. I use conservative sharpening settings when I'm working with HDR images, because the tone-mapping process tends to exaggerate micro-contrast. Always view your image at 100% magnification when you are applying sharpening, as you want to make sure that you don't create any ugly artifacts. If you wish, you can also apply other effects to the tone-mapped image. One of my favorites is the Tonal Contrast filter, found in Nik's Color Efex Pro 3 plug-in.