...simply a fusion of exposures. The same view is taken 3 or several times with different exposures. I proceed to an assembly of thesepictures afterwards with the help of a software. Photoshop, PaintShopPro or a dedicated one like Photomatix. The results are really impressive, especially when the light conditions are extremly difficult. Of course, like any special effect, this might become boring, picture after picture. So not to use endless.