HDR, short for High Dynamic Range, is a technique used by photographers to get the “right exposure” of a photo from a set of differently exposed photos. Ok, ok … what the heck for and is the word “right exposure” the right term?
Most cameras (and in fact, the human eye as well) are not able to capture the whole range of light that exists in the real world. By combining various photos of varying highlights, mid-tones and shadows, an image of higher dynamic range can be achieved. Typically a range that’s about 2 times.
A good example can be found at the photomatix website where they showed a set of picture taken from dark room with a window to the bright outdoors.
As can be seen from the 5 different exposures, it is almost impossible to get a balanced exposure for the picture. If metered on the outdoors, you will get an underexposed interior shot but if metered on the interior, you will get an overexposed exterior shot. HDR helps to give a more dynamic range. I like this particular example as I believe it gives us a clear explanation though pictures. A picture is as good as a thousand words, some say …