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.
It's 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.
Available effects are SSAO, SSIL, Depth Of Field, Lenz FX, Bloom, HDR, Tone Mapping, Sharpening, Vignette, Sun Rays, Shadows, Detailed Shadows, Reflection and other in various versions of it.
ENBoost is patch from ENBSeries which reduce memory usage of the games, so you may install much more modifications without crashes and errors, also it better utilize video memory of modern videocard.
Modern complex effects of top games are under your control.
Mod use true HDR, not fakes like implemented in many games.
Don't like post processing filters and colors in the games? Change it yourself.
Compatible with many games, even if not developed for them, just try it.
Some versions developed exclusively for specific game, then it's totally change the game.
Allow to customize games visually by anyone, we all have own taste and that's important.
Users share own presets on the ENBSeries forum or other sites, feel free to download them.
Many indie games use ENBSeries and even have exclusive versions of the mod.
Small size is a code with minimal amount of textures or without them.
Most important shaders available for editing, this allow to create custom graphic effects.
Other d3d9 modifications can be used together by configuring proxy feature.