HDR Photography By Jakub Kubica

Contrast ratio = 2(EV difference)
EV difference = log2(Contrast ratio)
The fact that an increase of 1 EV indicates a doubling of light means that EV is often represented on a base-2 logarithmic scale.
This concept is expressed mathematically as c = f (u, v). So the image plane is the domain, while the color space is the range of function f . Because we are concerned with digital images, this abstract mathematical description needs a concrete representation that can be processed by a computer and imaging devices, such as a digital camera or a monitor. To this end, the nature of digital technologies requires a discrete (binary) representation. So, our continuous mathematical model of the image function has to be discretized. This is done though a discretization of both the domain and range of the function f .