To be honest, I had never heard of HDR (or HDRI) until the iPhone 4 came out. It wasn’t until today that I learned that the initials stand for high-dynamic-range imaging. The only reason I know now is because of my new favorite photo app – Dynamic Light.
Since I’m learning about HDR for the first time, I’m not going to try and explain it. According to Wikipedia:
High-dynamic-range imaging (HDRI or just HDR) is a set of techniques that allow a greater dynamic range of luminance between the lightest and darkest areas of an image than current standard digital imaging techniques or photographic methods. This wide dynamic range allows HDR images to more accurately represent the range of intensity levels found in real scenes, ranging from direct sunlight to faint starlight.