High dynamic range imaging are sets of methods in photography and image editing that allows for a large range of exposure between light and dark areas. The goal of HDRI is to reproduce as faithfully as possible the wide range of intensity levels found in actual scenes. Very often, real scene have exposures ranging from direct sunlight to very dark and shadowed areas. Below is an example of an HDR image.
By changing shooting parameters such as shutter speed, many digital cameras can vary the amount of light they let in. Basically HDRI uses this characteristic of the camera to create images that are composed of multiple exposures. Doing so create images that greatly exceed the dynamic range of any single exposure.
Process-wise, the HDR procedure starts with blending several exposures of a particular scene into a 32-bit HDR source file. This file is then mapped tonally to produce an image in which the contrast and qualities of light can be adjusted in a localised manner. As a result of this, HDRI can create incredibly stunning and rich imageries.
So much for the technicality of HDRI, where can tools for be HDRI found? Well, there is a free software that can create HDR images from your photos that are taken at 2 different exposures. This software is call Photomatix Basic.
HDRI has application in the area of computer graphics as well. It is often used by 3D rendering programs as a Global Illumination solution.
Photomatix Basic is a very useful freeware for HDRI. It allows one to create High Dynamic Range Images from 2 photos of different exposures. Photoplus is another program that can create stunning HDR images.
Photomatix can intelligently tone map HDR images. Tone mapping is a technique applied to digital images so that tonal information can corresponds more closely to the way our eye perceives brightness.
Photomatix Pro is the paid version that has more features and control over the freeware version. If you are into High Dynamic Range photography, you should check out this program.