There’s a common misunderstanding about what HDR (High Dynamic Range) photography actually means, and what it was designed to do. HDR is often confused with tone mapping, a technique that simulates an extended dynamic range by reducing contrast in an image while brightening and saturating colors. Tone mapping is a way to tackle overly high contrast images, but the effects are frequently exaggerated with a grungy, garish look.
Look at just about any forum for photography and you’re practically guaranteed to see images that suffer from indelicate tone mapping. This is common in architectural and landscape photography, because this software technique helps overcome difficult lighting, bringing back the appearance of details in the shadow areas of an image, making them easier to read. Likely you’ve seen these photos, they look as if everything in them has an odd, neon glow. They’re vibrant, they’ve got details in the shadows, but they don’t look anything like the real world.
What Is Dynamic Range?
To understand true HDR photography, we first need to understand the concept of dynamic range. In photography, dynamic range refers to the values of light that a camera sensor can record, from the brightest highlights to the deepest shadow details and everything in between.
Even the best sensors can’t capture the full range of available light that the human eye can see, so we, as photographers, have to decide (or let the camera decide for us) the best exposure—best being the exposure that will retain as much detail as possible at both ends of the range. In most cases, this will mean slightly underexposing the image in a high-contrast scene. Why? It’s possible to bring back at least some details in the shadow areas of an image in post processing, but if your highlights are overexposed and blown out, no software can bring back the detail because there’s no data to manipulate; it’s just pure white.
There’s a way to overcome this limitation, and that’s HDR.
True HDR photography involves combining the data from multiple bracketed exposures to restore detail at the extreme ends of the tonal range. The most basic HDR image is built from three exposures: one “normal” exposure, one overexposure to increase shadow detail and one underexposure to retain detail in the highlights.
A simple bracket of -2 EV, 0 and +2 EV typically will provide good results. It’s important to note that when shooting these bracketed exposures, you need to be on a tripod and ensure that there’s no camera movement between exposures, otherwise details won’t line up when you composite them.
Creating The HDR Composite
There are many good applications for creating HDR composites, such as HDRsoft Photomatix (hdrsoft.com), Aurora HDR from Macphun (macphun.com) and Unified Color’s HDR Expose (unifiedcolor.com). The ability to create true HDR images is also built into recent versions of Photoshop and Lightroom, which I’ll walk you though.
In Photoshop, go to File > Automate > Merge to HDR Pro to launch the built-in HDR tool. You’ll be asked to select your files, then Photoshop automatically creates the composite. Next, you’re presented with several possible adjustments, including Exposure, Detail and Saturation, to fine-tune the result. When you like the look of the composite, Photoshop will assemble it into a final file.
The HDR software packages all approach HDR photography slightly differently and all have a wide range of controls for creating a (hopefully) perfect final image. Ideally what you want to end up with is a file that has good looking detail in the highlights, the midtones and the shadows, without color casts or areas of poor contrast.
HDR photography isn’t something you need every day. Careful exposures, in most cases, will result in beautifully detailed images, but when trying to handle extreme contrast, knowing this technique will help you hold details that would be lost in a single exposure.
To see more of Jim Nix‘s photography, visit nomadicpursuits.com.
Updated August 2, 2016
Published August 4, 2014