Exposure Fusion Technique

There are several methods and techniques that real estate photographers use to create beautiful images. While each may be a little different, they all require an initial shoot followed up by some amount of post-processing using various software tools. No one method is necessarily better than another if used properly, and all focus on creating beautiful images that show off the home at its best.

I use a method known as Exposure Fusion, which is a technique for blending multiple bracketed exposures of the same scene into a single image. Simply explained, multiple photos (usually between three and seven) of the same scene are taken in sequence using different exposures. For example, if three exposures are taken, one image is underexposed, one is properly exposed, and one is overexposed. Those images are then blended together to form a final single image.

The purpose of bracketing is to increase the dynamic range of the photograph from the shadows to the highlighted areas. Using the Exposure Fusion technique, an algorithm identifies the best “bits and pixels” from each image in the sequence that will produce the most correct exposure. Those "bits" are then seamlessly combined to create a final “fused” image. The goal of this technique is to create a final image that is more realistic to the actual subject and what the human eye actually sees.

As an example, bracketed sets of the images shown below were taken at three different exposures. The first images are properly exposed and look pretty good. However, the shadowed areas are a bit dark and lose some detail, and some of the brighter areas are too bright and lack detail.

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The next images were underexposed to capture detail in the highlighted areas. The sky and clouds are nicely exposed, as well as the scene outside the kitchen window, but the shadowed areas are almost completely lost.

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The final images were overexposed to capture the detail in shadowed areas. In these images, however, the highlights are completely blown out.

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By combining these bracketed images, the resulting photographs are properly exposed, and all of the details in both the shadowed areas and highlights are captured correctly. A small amount of additional post-processing was performed to ensure proper white balance and color.

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Exposure bracketing is particularly useful in interior photography, in which lighting tends to be uneven from one side of a room to another. It enables the photographer to represent the room with even lighting and capture details that would otherwise not be visible. Bracketing can also be used for exterior photography, and is especially useful on very bright days. It enables the photographer capture the highlights in clouds and bright, blue skies, as well as bring out details in portions of the structure that are shadowed.

High Dynamic Range (HDR) Photography and Tone Mapping

Exposure Fusion is not a type of HDR photography, although the two are frequently confused and sometimes used interchangeably.

The HDR method is similar to the exposure fusion method in that it also requires the generation and blending of multiple exposures to correctly capture the highlights and details. However, the HDR method requires an additional step known as tone mapping, which is essentially converting the tonal values of an image from a high range to a lower one, with the same goal of creating a final, correctly exposed image.

While the exposure fusion method maintains a certain amount of shadows and highlights more realistic to what the human eye can see, tone mapping evens out the tonalities in the image and can sometimes result in a loss of contrast and uneven transitions between the shadows and highlights. Tone mapping can also significantly enhance detail and colors, which sometimes results in images becoming very surreal looking and “over cooked” if not applied properly.

HDR is frequently used for artistic expression in fine art photography. Great examples of this technique can be found in images of landscapes, particularly at sunrise or sunset, abandoned structures, antiques, and rusted objects, including cars, boats, trains, etc. Using the HDR technique, cloud formations become well defined, the colors of sunsets and flowers are much more vibrant, and images can be made to “pop”. HDR is a very effective form of photography when used properly, but can be overdone when used for architectural photography.