ENBSeries is 3d graphic modification for games like TES Skyrim, GTA 4, GTA San Andreas, Deus Ex HR, FSX, and many others. It work by modifying render functions calls of the games and applying additional effects.
ENBSeries divided to generic versions and exclusive. First category allow to run it on thousands of games, not all effects will work, but you can try several versions of mod to find best suited. Second, exclusive types of the mod, are games specific versions which developed to work with some game and rarely with same game engine.
ENBSeries have SSAO, SSIL, Depth Of Field, Lenz FX, Bloom, HDR, Tone Mapping, Sharpening, Vignette, Sun Rays, Shadows, Detailed Shadows, Reflection and other effects in various versions of it.
Following screenshots are from various presets for the mod created by users, click to enlarge