One of the most fundamental technical challenges in photography is controlling contrast. The contrast between the brightest highlights and the darkest shadows in a scene is the “dynamic range.” Our eyes can accommodate greater dynamic range than our digital cameras can. This presents a problem when trying to capture images in contrasty light and make them appear more like what our eyes can see.
In low contrast light—such as on cloudy days or after dusk when the sun is below the horizon—it’s easier to make good exposures that retain detail in highlights and shadows, as well as everywhere in between. That’s why photographers so often shoot at such times. When we have to work in contrastier light, though, one way photographers lessen that contrast is to add light—a fill light from a reflector, for instance—to make the darkest shadows a little lighter and tighten up the dynamic range.
But in some instances, adding additional lighting to minimize contrast is impractical. In architecture, landscape or travel photography, for instance, the scale of the scenes makes them impractical to light. So you need another method to control contrast, and it comes in the form of multiple exposures.
If we rely on a single exposure in a contrasty scene where the dynamic range exceeds that of our camera’s sensor, we’ve got to make a fundamental choice: do we overexpose to illuminate shadows (resulting in blown out highlights) or underexpose to bring down those highlights (resulting in lost detail in the shadows). When either end of the spectrum contains detail you’d like to see, you’ve got a problem.
Enter high dynamic range exposure layering. High dynamic range (HDR) processing combines multiple exposures of the same scene, choosing highlight detail from the darkest frame plus shadow detail from the brightest frame to add to the normal exposure for more detail and (you guessed it) the appearance of higher dynamic range.
HDR is often associated with a particular overprocessed look embodied by cartoon colors, luminance halos and generally obnoxious digital images. Taste is of course subjective, but to many (including this author) the look is, frankly, awful. It was the result of overdone “tone mapping” using algorithms to assign luminance values in an effort to fit a higher dynamic range scene (i.e. the real world) into the limited range of a digital image file. Done aggressively, this overcooked tone mapping look is why so many folks still associate HDR with awful looking images.
But HDR can be so much more—especially by doing so much less. HDR can be used to a more subtle end when it is applied for something simpler: basic contrast control. With just a bit of HDR processing you can bring up shadow detail or bring down highlight detail and make an image more readable without turning it into a cartoon. While serious HDR artists may prefer specialized software for their most intensive processing, the rest of us who want to keep our images looking reasonable can do our kind of HDR exposure layering quickly and effectively in Lightroom.
Starting with two or more RAW image files (use RAW because their already heightened dynamic range works much better for this than JPEGs) open Lightroom’s Develop module. Find the images you want to layer in the thumbnails and click to select the first image in the range, then shift-click on the second image (or the last in the range and you will have selected all of the files in between). Because it doesn’t take much to create a noticeable contrast improvement, just two files may be sufficient if they’re a couple stops apart in exposure value. (The examples shown here come from two frames just under three stops apart in exposure value.) The higher the contrast range, the more exposure you will need in theory–although two or three images is often enough to see significant improvement in many scenarios.
Let’s detour for a moment to briefly talk about the importance of tripods. If you’re going to combine multiple exposures into a single HDR image, those compositions need to be identical in every way except for the exposure. This is achieved with a camera locked down on a tripod. If you can’t affix the camera to a tripod, do your best to hold the camera as steady as possible between exposures so Lightroom or Photoshop will have a better time aligning them during processing. But even if your camera is locked down tight, remember that any moving element in the image—like the paddleboat in the samples shown here—won’t composite correctly and will create a ghosted image that will need to be dealt with. If the problem is significant you can always use a layer mask in Photoshop to repair such ghosting, but in the image here simply adjusting the deghosting amount in Lightroom’s HDR Merge window largely solved the problem.
Having selected two or three image files of differing exposures in Lightroom, go to the Photo menu at the top of the screen and look for Photo Merge just below the Edit In heading of the menu. Hovering your mouse over Photo Merge, a new menu appears and offers the HDR option. Click it and the images will open within Lightroom’s HDR Merge Preview window.
From here, the process is super simple. Click the checkbox to Auto Align if your images were captured handheld, and check Auto Settings to let Lightroom have a go at guessing the correct exposure. Then choose the deghosting strength—low, medium, high or none—in order to try to minimize misalignments. Lastly, check or uncheck the Show Deghost Overlay option to see where Lightroom is working to address those misalignments, and then check the Create Stack checkbox to load the finished HDR DNG file into a stack within Lightroom along with the original RAW image files.
Having completed the HDR merge you’ll notice that Lightroom maintains the new image file as a RAW DNG file. This means you can easily dial back things that don’t look quite right to your eye—another great preventative for the awful, overcooked HDR look. Maybe it just takes a little less saturation, or a little more highlight detail, or perhaps less shadow detail. All of the typical RAW image controls remain viable with a Lightroom HDR merge, making it a quick and easy way to improve contrast without resorting to dramatically bad HDR.
