HDRI Photography – A New Technique For The New Age

“Oh Comon’. Take A Shot At It.”

“‘Cause I’m Lonely?”

The first time I saw an HDR Image I was blown away. However, I was convinced that it had manipulated in some way to just make it look cooler. But that is not the case at all my friend. Not the case at all…

HDRI is a set of techniques that allows a greater dynamic range of exposures (the range of values between light and dark areas) than normal digital imaging techniques. The intention of HDRI is to accurately represent the wide range of intensity levels found in real scenes ranging from direct sunlight to shadows. The desirability of high dynamic range imaging (HDRI) has been recognized for decades but its wider usage was, until quite recently, precluded by the limitations imposed by the available computer processing power.

HDRI was originally developed for use with purely computer-generated images. Later, methods were developed to produce a high dynamic range image from a set of photographs taken with a range of exposures. With the rising popularity of digital cameras and easy-to-use desktop software, the term “HDR” is now popularly used^[1] to refer to the process of tone mapping together with bracketed exposures of normal digital images, giving the end result a high, often exaggerated dynamic range. This composite technique is different from, and generally of lower quality than, the production of an image from a single exposure of a sensor that has a native high dynamic range. Tone mapping is also used to display HDR images on devices with a low native dynamic range, such as a computer screen.

One problem with HDR has always been in viewing the images. Mundane CRTs, LCDs, prints, and other methods of displaying images only have a limited dynamic range. Thus various methods of converting HDR images into a viewable format have been developed, generally called “tone mapping”.

Early methods of tone mapping were simple. They simply showed a “window” of the entire dynamic range, clipping to set minimum and maximum values. However, more recent methods have attempted to show more of the dynamic range. The more complex methods tap into research on how the human eye and visual cortex perceive a scene, trying to show the whole dynamic range while retaining realistic colour and contrast.