Therefore, revealing detail in the darkest of shadows requires high exposures, while preserving detail in very bright situations requires very low exposures. Conversely, a decrease of one EV represents a halving of the amount of light. An increase of one EV, or one stop, represents a doubling of the amount of light. In photography, dynamic range is measured in exposure value (EV) differences, known as stops. Photography Dynamic ranges of common devicesįour-thirds DSLR camera ( Panasonic Lumix DC-GH5) Non-HDR cameras take photographs with a limited exposure range, referred to as low dynamic range (LDR), resulting in the loss of detail in highlights or shadows. Outside of this range, no features are visible because there is no differentiation in bright areas as everything appears just pure white, and there is no differentiation in darker areas as everything appears pure black. Standard photographic and image techniques allow differentiation only within a certain range of brightness. The brain continuously interprets this information so that a viewer can see in a wide range of light conditions. The human eye, through non-linear response, adaptation of the iris, and other methods, adjusts constantly to a broad range of luminance present in the environment. One aim of HDR is to present a similar range of luminance to that experienced through the human visual system. 2.2 Comparison with traditional digital imagesĮmulating the human vision system."HDR" may refer to the overall process, to the HDR imaging process, or to HDR imaging represented on a low-dynamic-range display such as a screen or standard. This method reduces the overall contrast of an HDR image to facilitate display on devices or printouts with lower dynamic range, and can be applied to produce images with preserved local contrast (or exaggerated for artistic effect). The method of rendering an HDR image to a standard monitor or printing device is called tone mapping. Due to the limitations of printing and display contrast, the extended luminosity range of input HDR images has to be compressed to be made visible. HDR images can also be acquired using special image sensors, such as an oversampled binary image sensor. The two primary types of HDR images are computer renderings and images resulting from merging multiple low-dynamic-range (LDR) or standard-dynamic-range (SDR) photographs. High-dynamic-range (HDR) images are often created by capturing and then combining several different, narrower range, exposures of the same subject matter. HDR is useful for recording many real-world scenes containing very bright, direct sunlight to extreme shade, or very faint nebulae. The ratio between the maximum and the minimum of the tonal value in an image is known as the dynamic range. Outside this range, no features are visible because in the brighter areas everything appears pure white, and pure black in the darker areas. Standard techniques allow differentiation only within a certain range of brightness. In photography and videography, HDR or high-dynamic-range imaging is the set of techniques used to reproduce a greater range of luminosity than that which is possible with standard photographic techniques. Kentigern's Church in Blackpool, Lancashire, England Tone mapped high-dynamic-range (HDR) image of St.
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