I recently came across the term DRI meaning Dynamic Range Increase.
What exactly is it and how does it differ from HDR or High Dynamic Range (or is it the same thing just different terminology?
DRI is Fred Miranda's approach to (and software for) HDR.
There was a time when high dynamic range images were spoken of in polite company. Essentially, it just means any method of combining different exposures to capture more detail in the shadows and highlights of a finished image than you could have gotten with a single exposure, and it was probably most commonly used in astrophotography.
Over the past few years, the term "HDR" has become associated with heavily tone-mapped images displaying flat, often desaturated colors, a lot of textural detail emphasis, and "halos" around areas of great tonal difference. HDR images don't have to look like that, no matter what software you use, but the overprocessed look has become something of a fad. The name "DRI" is there to differentiate what Miranda's software does from the fad look.
You can achieve high dynamic range images that don't look overprocessed in a number of ways. This article over at Luminous Landscape describes a few of them; I generally use multiple, separately-processed layers and layer masking (using Topaz ReMask, though I have used OnOne Perfect Mask and Corel Knockout in the past).
Apparently there's a difference, as evindenced by the DRI group on Flickr which advertises "DRI only, no HDR". That group apparently advocates manual blending of exposures as opposed to merging to an intermediate high dynamic range image and then tonemapping down to a standard dynamic range image for display purposes.
However, personally I'd rather use a single term for all processes which take multiple images with different exposures and produce a result that would not be possible in camera with a single exposure. I don't get why it matters whether an intermediate representation existed or didn't exist, it's the final result that matters.
HDR, DRI and exposure fusion can all be done well or done badly. It seems to me like people invent terms to escape the stigma that is (arguably deservedly) attached to "HDR images" whilst doing something extremely similar (but better executed).