Given the limitations of film and sensors in capturing the enormous dynamic range of visible light that occurs in nature, it’s impossible to capture the subtle nuances of highlight and shadow detail in a single exposure.
A traditional in-camera workaround has been to use a graduated neutral density filter to reduce the exposure in the lighter areas, while allowing the full amount of light to enter the camera in the darker areas. This works fairly well if you’re photographing a landscape with a straight horizon or similar linear break between lights and darks. There are also spot-type filters with a darker neutral-density area in the center.
The first attempt at addressing the dynamic range issue in digital photography, either in camera or in post-processing, has been through the Shadow/Highlight filter, also known as:
- ADL (Active Dynamic Lighting, Nikon)
- iContrast (Canon)
- Recovery/Fill Light (Adobe Camera Raw)
- Shadow/Highlight, (Adobe Photoshop)
These cameras use algorithms which incorporate a high-pass filter to mask out the problem areas and restore detail by adjusting their brightness or darkness.
These methods however are all based on a single exposure. HDR photography is based on taking multiple exposures and combining them dynamically into a single image through the use of HDR software. However, this same concept can also be applied without the use of such software by bracketing exposures and combining them as fully masked layers in Photoshop, revealing the areas with the desired detail.
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