Translated from Wikipedia:
In image processing, computer graphics, and photography, High Dynamic Range Imaging HDRI or high dynamic range imaging (or just HDR) is a set of techniques that allows a wider dynamic range between light and dark areas of an image than standard digital imaging techniques or photographic methods today. Dynamic Range, which allows the width of captured images HDR more accurately represent the range of intensity levels found in real recordings, ranging from bright sunlight to faint starlight faint
The two main sources of HDR imagery is a computer renderings and merging of multiple Low Dynamic Range (LDR = Low Dynamic Range) or standard- dynamic range (SDR) photographs. Tone mapping techniques, which reduce overall contrast to facilitate display images HDR on devices with lower dynamic range, can be applied to produce images with preserved or exaggerated local contrast for artistic effect.
In photography, Dynamic Range is measured in EV differences (known as stops) between the light and dark parts of the image that show detail. Increasing one EV or one stop = twice the amount of light
Photo by Height Dynamic Range is generally achieved by taking some photos of the standard, often using exposure bracketing, and then combines them into an image HDR. Digital photographs are often encoded in RAW format, because 8 bit JPEG password does not offer enough values to allow for smooth transitions (and also introduces undesirable effects due to loss compression). Loss compression is a compressed data code by removing some parts.
Each camera can be programmed Manual and can be made over exposure or under exposure photographs, can be used to create HDR images.
Some cameras have an automatic exposure feature (AEB = Auto Exposure Bracketing) with Dynamic Range is much larger than the others, from the 3 EV of the Canon EOS 40D, with 18 EV of the Canon EOS-1D Mark II. Increasingly popular imaging techniques, some manufacturers are now offering HDR camera features. For example, the Pentax K-7 DSLR has HDR mode that captures images HDR and then outputs (only) a tone JPEG file. Canon PowerShot G12 and Canon PowerShot S95 offer similar features in a smaller format.
Editing of all imaging results is one of the demands required by Highest Dynamic Range. Editing operations need high precision to avoid the effect that causes different signals become indistinguishable as banding and jaggies. Photoshop users are familiar with the issues Low Dynamic Range current. With 8 bit channels, if you brighten an image, information is lost can’t be taken back: dark picture after brightened not restore the original appearance. Instead, all the bright light seemed flat and erased. We must work carefully to avoid this problem.