Single Exposure HDR

HDR (High Dynamic Range) photography is a software technique primarily intended for combining bracketed exposures to generate a single image from the best exposed parts of each individual exposure. This makes it possible to produce a well exposed image in challenging light situations.

Bracketed shots: Normal – Underexposed – Overexposed

The normal exposure above is just an “okay” shot (click image to view full size – then Back). But to get the shaded porch exposed correctly, the bright background and sky detail is completely blown out. The underexposed shot brings out that detail, and the overexposed shot gets detail from the heavily shaded roof of the porch.

HDR Result

Combining the three shots with HDR software results in the image above, showing well-exposed detail in all of the lighting situations posed by the scene.

Single Exposure HDR

So that’s what HDR software is meant for. But, it can also be used on a single image. The controls you have over the tone mapping process used in HDR can create some very dramatic effects, even when applied to a single image. Here are a couple of examples where HDR software was applied to a single image.

Before HDR
Before Before

After HDR
After After

Raw Helps

By the way, the other thing that contributes to the success of this, especially when having only a a single image to work with, is that I shoot in “raw.” The more common JPG compression throws pixels away and limits the amount of enhancement one can perform. In the raw format, all the data from the photo detector is stored unmodified. That is kind of a double-edge sword, in that post processing is almost always required to enhance an otherwise unimpressive image. On the other hand, since the data is there, it makes it possible to do more enhancement and achieve an even higher quality image with the post processing you do.

The old locomotive above is an excellent example of that. In the original image, the stack looks almost completely black as it is back lit against the bright but bland gray sky. A primarily black subject back lit against a bright sky… a terrible exposure situation. Yet, the HDR software was able to pull out color and detail that is contained in the raw image, thus saving the picture.

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