High-dyanmic-range (HDR) imagery evolved as a way to compensate for a camera sensor’s inability to capture full details from scenes with a high luminance range.
Simply, shadows are rendered as indistinguishable black tones, devoid of contrast, and highlights are similarly clipped at pure white tones when the dynamic range is greater than your camera can handle.
Extreme lighting conditions exist when a wide variance of brightness values exist. Often, the most extreme luminance ranges are created from intense light sources illuminating objects that in turn cast their own shadows, further diversifying the light spectrum.
The problem cameras have in capturing broad luminance spectrums is similar to the limitations of their focusing systems. Cameras can only focus on a single plane and can likewise only meter for exposure in a limited area.
In the above image, I metered the exposure by focusing on the highlights present in the building’s dome. The dome itself is exposed perfectly, but the remainder of the scene is much too dark. If I meter for the columns, the dome loses its detail and becomes a blown out blob of white.
The solution to this problem is capturing multiple instances of the same scene with different exposure settings. You’ll most likely need a tripod for this to ensure a blur-free image. Additionally, don’t forget to turn off your autofocus after the first shot so that your camera doesn’t shift its focus in subsequent frames.
The resulting image is a composite of data from seven frames, from two stops underexposed to four stops overexposed.
You can create the composition manually in an image editing program, by using an editor’s automated script, or by purchasing a dedicated HDR program or plugin.