What is HDR

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2016-06-13 01:53

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Edited by baymax2000 at 2016-06-13 05:33

What is HDR?


HDR stands for High Dynamic Range imaging, and it's an old photography practice recently introduced to camera phones like the iPhone and some Android devices (or with the use of special apps). You're on the right track it's supposed to make your pictures look better, but it depends on when you use it. Here's a quick primer on how HDR works, and when you should—and shouldn't—turn it on.




How it Works.!!


AHDR, as its name implies, is a method that aims to add more "dynamic range" to photographs, where dynamic range is the ratio of light to dark in a photograph. Instead of just taking one photo, HDR uses three photos, taken at different exposures. You can then use image editing software to put those three images together and highlight the best parts of each photo. In the case of HDR on smartphones, your phone does all the work for you—just take your picture and it will give out one regular photo and one HDR photo. The result is something that should look more like what your eyes see, rather than what your camera sees.








This is why, when you turn HDR mode on, your phone takes a little longer to take the photo. It's actually taking three pictures at a time, rather than just one. Check out the image above for an example.


HDR Sensors


More and more CMOS image sensors now have high dynamic range capability within the pixels themselves. Such pixels are intrinsically non-linear (by design) so that the wide dynamic range of the scene is non-linearly compressed into a smaller dynamic range electronic representation inside the pixel. Such sensors are used in extreme dynamic range applications like welding or automotive.


[font="Some other sensors designed for use in security applications can automatically provide two or more images for each frame, with changing exposure. For example, a sensor for 30fps video will give out 60fps with the odd frames at a short exposure time and the even frames at a longer exposure time. Some of the sensor may even combine the two images on-chip so that a wider dynamic range without in-pixel compression is directly available to the user for display or processing.


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