What does HDR mean? What does the iphone HDR mode mean?

What does HDR mean?

High dynamic range images (high-dynamic range, or HDR), which can provide more dynamic range and image details than ordinary images, based on LDR (Low-dynamic range) images of different exposure times, The final HDR image [1] is synthesized using LDR images with each exposure time relative to the best detail, which can better reflect the visual effects in the real environment.

Concept

As described above HDR, for the short name of a high dynamic range, what is a high dynamic range, for example:
The real reality of the brightness difference, that is, the brightest object brightness, and the smallest object brightness ratio, and the human eye can see the range is about, but the general display, the camera can represent only 256 different brightness.
But we can take a few more pictures, 2, 3, ..., even dozens of, these photos of the exposure in turn increase, many friends should be able to think, as the photo exposure increases, the photos will turn bright, in another way, the details of the photos will change from the bright to the dark.
According to the principle above, if we combine many of the pictures taken by the camera, the order of magnitude of the picture is generally even more.
This problem arises, or a higher order of brightness can only exist in the computer, and the general display can only represent a level of brightness, with 256 numbers to simulate the information can be expressed, this simulation method is the core of HDR technology, named Tone-mapping[1]. With tone-mapping compression, our synthesized HDR image can be well displayed on the display, which can give people a shocking effect.

What does HDR mean in a camera photo? is actually a post processing technology. HDR (highly dynamic range imaging, English: High Dynamics Range Imaging, abbreviated HDRI, or HDR) is a set of techniques that are used to achieve a greater exposure dynamic range (i.e., greater light and shade) than ordinary digital image technology.

Dynamic range is the highest and lowest value of the relative ratio of electrical signals, reflected in the photo is the highlight area and dark areas can be displayed in detail, the more dynamic range of the more rich. The goal of high dynamic range imaging is to correctly represent the large range brightness in the real world from sunlight to the darkest shadow. To put it simply is to let your photos regardless of the high light or shadow part of the details are very clear, try to make the effect of the photo close to the eye of the effect.

In order to get the image effect of HDR, it is not enough to take a photo, and a series of photos with different exposure values will be taken, which can be combined into a high dynamic range of photos by software. In the age of film photography, people have been able to increase and decrease the level of light and dark position of the photo by local illuminate (Dodge) or dimming (Burn) during the darkroom flushing. Although there are few opportunities to reach the darkroom, dodge and burn two tools can be found in Photoshop to simulate the effects of local lighting or dimming in the darkroom. Using HDR technology, you can break the limit of latitude, bring the level of photos to an unprecedented level, and further broaden the space of photography creation.

Photo HDR Front (left) after contrast

With the growing popularity of digital cameras and mobile phone photography and the ease with which desktop software becomes available, many amateur photographers and ordinary consumers are happy to use a high dynamic range imaging method to produce photos of high dynamic range scenes, but do not use this as its only purpose, but there are many other applications in the high dynamic range.

For example, when used for display, high dynamic range images are often tonal mapped and are used with several other full-screen display effects (full screen effect).

Believe you know what HDR is now, right? HDR is a group of more than ordinary digital image technology more exposure to the dynamic range of a later technology, in a word, is to enhance the dark part of your photos, reduce the brightness of the light, so that the overall picture picture more vivid