Exposure fusion is a technique for blending multiple shots of the same scene into a single image. Each shot is aimed at providing a "good" exposure for a region of the scene.
Multiple shots can be obtained by using the bracketing mode of your camera, or by applying different sets of adjustment layers to a single image with bLUe. read.. The layer stack of bLUe is very handy to load multiple images with only one click and to (eventually) apply some adjustment layers to each image. Next, adding a Merging Layer to the stack and selecting the layers to merge do the job.
1 Open an image file. Next, from the Layer menu choose New Image Layer(s)->Load Image(s) From Files. In the File Dialog which pops up, select the image files to load (Ctrl-Click for multiple selections) and press Open.