Saturday, August 14, 2010

HDR Photography

In photography, Dynamic Range is the extent between the darkest and the brightest objects that the camera can capture.  Dark objects outside of the range will be rendered as black without any details.  Conversely, objects brighter than the range will be completely washed out, also with no details.  Film is generally thought of as having a higher Dynamic Range than digital.  However, at the end of the day, it also depends on the Dynamic Range of the medium the photograph is rendered. Be it photographic paper, computer monitor, etc..

Due to this finite Dynamic Range, a photographer must choose the correct exposure for the main object of the photograph.  Consider the scene in picture 1.

Picture 1

Here the exposure is set for the foliage outside (1/80 sec, F/11, EV -1.3 step).  The flowers in the foreground are completely dark.  Picture 2 is at the opposite end of the range.

Picture 2

In the second picture the flowers in the foreground are properly exposed but the foliage outside is completely washed out (1/5 sec, F/11, EV + 1.3 step).

High Dynamic Range (HDR) photography is a technique to increase the dynamic range of a photograph by combining multiple pictures of an object taken at different exposure levels.  Most modern digital cameras have a feature called Auto Bracketing.  When activated, the camera will take 3, 5, or 7 successive pictures at different EV levels.  The result is multiple shots of the same object at different EV levels.

There are software tools that can take these multiple exposure shots and combine them into a composite HDR picture.  Photomatix is one, Oloneo is another.

The following is an early HDR experiment that I did using the beta version of Oloneo. 
  1. For the scene I selected a vase of flowers on the living room coffee table. Outside the window is a bright New England summer morning.
  2. Using a tripod, I took two sets of 5 auto-bracketed shots with my Lumix GH1.
  3. The 10 pictures I then imported into Oloneo as an HDR Tonemap project.
  4. Slide a couple of buttons and: Voila! An HDR composite was created.
Picture 3 shows the HDR composite that was created by Oloneo. It shows a properly exposed foliage outside the window as well as bright flowers inside.  The series of pictures on the left hand column are three of the ten pictures that were used for the composite.

Picture 3
(click here for high resolution version )

In summary, HDR photography is quite accessible to the masses.  It is made possible by the ubiquitous auto-bracketing feature of digital cameras and by HDR compositing software.  Oloneo is quite easy to use, even to the complete newbie to HDR.

Related HDR links:

And here is a very early form of HDR circa 1910:

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