The term HDRI stands for High Dynamic Range Imaging, and refers to the techniques used to capture images where there is a wide range of lighting levels in a scene.
Human Vision = Wide Range
The human eye has a very wide light perception range. We can clearly see the details inside a room, and simultaneously see the clouds and bright sky outside the window.
Imaging Device = Narrow Range
An imaging device, such as a film or digital camera, cannot do this. If we take a picture of the same scene, we will either get a clear room interior with a washed out sky through the window, or a detailed sky with a very dark room detail, but not both. The problem resides in that the camera’s film or digital sensor cannot accomodate the bright outside with the dim inside at the same time. This is what is called a narrow dynamic range.
In order to obtain an image that reproduces what we observe with our own eyes, we would need to compress or re-map the light levels of the real world down to the small range of the device, such that all light levels are given sufficient luminous range.
The series of techniques used to accomplish this feat, are called HDR or HDRI.
Multiple Exposure HDR
One way of doing it is to take several pictures of the exact same scene but using different exposure levels so that in each picture we focus on a segment of the whole light range. This process is commonly referred to as bracketing.
Imagine we first take a dark picture in which the sky through the window can be seen in full detail, with a nice saturated blue color and well defined clouds. Then we take another picture which is bright, where the room details are clearly visible. Finally we take those two pictures and through the use of sophisticated algorithms we combine the illumination levels of both so that we obtain an image where both the sky, clouds and room details can be seen with nice color saturation, contrast and detail.
The problem is that multi-exposure methodology is seldom practical for everyday use, as it entails a tedious process requiring a tripod, and then manipulating the images in the computer, aligning them and adjusting the tone mapping. It is also a process that is not suited for pictures that involve people, as most likely they can’t stand still long enough for the several pictures to be taken (in such case we would have to further refine the pictures to avoid ghosting when the images are composed).
HDR Reactor: single image pseudo HDR
This is why we developed HDR Reactor, so that you can apply the HDR technology to your everyday photos without the need of several exposures. HDR Reactor, uses specialized tone mapping algorithms to bring out the details lost in your image, enhancing contrast, color and overall image quality.
