HDR or High Dynamic Range photography is a broad term describing techniques to overcome the inability of cameras to capture the entire brightness range of a scene in one exposure. The term covers a range of techniques and processing workflows. The most common workflow is often called Tone Mapping and produces very punctuated colors and contrasts. Exposure Fusion is an automated approach that attempts to optimize contrast without affecting colors.
For an automated process, the photographer takes a series of images (exposure bracketing) with different brightness levels and loads them into software that will analyze the image and attempt to output an image that shows the entire brightness range by compressing or expanding the most light and dark areas. Since the software has no idea about what the scene should look like, the results can be poor. Extreme orange and blue hues, walls and other smooth surfaces looking smoke damaged or dingy are a couple of common problems.
HDR is not a new technique. Famous photographers such as Ansel Adams employed the same approaches to getting the whole tonal range in one print with advanced darkroom techniques. The same thing is done in the digital age and is often described as “hand blending”. The photographer makes a series of exposures and manually blends darker and lighter areas from one exposure into the final image to build a final photo.
The advantage of hand blending is the photographer has much more control over what parts of the image are manipulated and what parts are left alone. The goal isn’t to create extremely flat lighting, but to present an image, in real estate at least, that best captures the look and feel of a space. The disadvantage is that it takes more time and skill. It can be one of the only ways to build an image when it’s a bright day and the front of the home has a deep entryway. The photographer can make one exposure for the sky, one for the home and one for the entryway to be combined seamlessly. When software tries to do this, the look is flat, misty and pastel.
No one technique can address all of the challenges of photographing a home, but computer processed HDR is the least quality approach. It’s often adopted due to the low skill level required of the photographer and the automated nature of the post processing. It has a very hard time when lighting fixtures cast strong shadows. Automated HDR has problems when dealing with different light sources (LED, tungsten, florescent, daylight) present in the same scene. It should be considered as a last resort rather than a first choice.