Going HDR

In image processing,computer graphics and photography, high dynamic range imaging (HDRI or just HDR) is a set of techniques that allows a greater dynamic range of luminances between light and dark areas of a scene 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.


This method was 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 to refer to this process. This composite technique is different from (and may be of lesser or greater 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. Typical computer monitors (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 compress the dynamic range into one reproducible by the intended display device. The more complex methods tap into research on how the human eye and visual cortex percieve a scene, trying to show the whole dynamic range while retaining realistic colour and contrast.

Images with too much "HDR" processing have their range over-compressed, creating a surreal low-dynamic-range rendering of a high-dynamic-range scene. All these images are taken with 6 different exposures and I used Photomatix, a software that generates HDR images using Tone Mapping.