HDR is the abbreviation for high dynamic range. In digital photography, HDR refers to digital images that have a high dynamic range, higher than a standard digital camera image would normally capture. A HDR image is produced with software techniques that expand the range of illuminance of a standard digital camera image to more accurately represent the wide range of intensity levels in real life scenes.

To produce a HDR image, a scene is most commonly photographed several times with different exposure values, usually ±1 EV or ±2 EV apart. If this camera technique sounds very familiar, yes it would be. This technique is called exposure bracketing. Many cameras can do this automatically with a feature called Automatic Exposure Bracketing, or another similar terminology.

Probably the trickiest part about producing a HDR image from several images is that the camera and subject must remain still between each shot, and focus and depth-of-field kept constant. If not, when the photographed images are blended together in HDR software, the resulting HDR image may appear wrongly overlapped or blurred. A tripod must be used.

An alternative, perhaps unorthodox, method is to photograph a single image saved in the camera’s native RAW format (such as Canon CR2, Nikon NEF, Fujifilm RAF, etc), and from this single RAW format image, produce several images of different exposure levels to be blended into a resulting HDR image.

Unlike the JPEG format commonly and frequently used to save a digital image, the native RAW format contains much more image data. JPEG format files can only contain 24 bits of image data allocated to 8 bits for red, 8 bits for green, and 8 bits for blue. In comparison, RAW format files can contain 30 (10 bits per colour channel), to 42 bits (14 bits per colour channel) of image data. RAW format files allow photographers to greatly alter exposure levels and colour casts with minimal loss or damage to the digital image, but not so for the JPEG format. It is for this reason that professional and serious photographers prefer, and even swear by, RAW format in their paying assignments.

The above gallery contains HDR images photographed in July 2010 in Moama in New South Wales state (about 235km from Melbourne), and in October 2010 in Noojee (about 115km from Melbourne), Noojee State Forest, Toorongo Falls, and Walhalla (about 180km from Melbourne).

Scenery in HDR – part 2

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