Bloom (sometimes referred to as light bloom or glow) is a computer graphics effect used in video games, demos and high dynamic range rendering (HDR) to reproduce an imaging artifact of real-world cameras. The effect produces fringes (or feathers) of light extending from the borders of bright areas in an image, contributing to the illusion of an extremely bright light overwhelming the camera or eye capturing the scene.
Technically, bloom lighting dates back to the early days of video gaming when CRT displays were used. Lower-resolution CRT displays produced a natural hardware blooming effect, something that modern HD displays lack. Many older 2D games were designed around the blooming effects of a low-resolution CRT monitor, but as a result, many older 2D games end up looking worse on modern HD displays without the lo-res CRT blooming. For example, the dithering technique was used in conjunction with CRT blooming to simulate additional colors and transparency, which is no longer evident on a HD display.
The modern bloom lighting effect, in the sense of software-based filtering/shading, was introduced by the PS2 title, The Bouncer, released in 2000, which used it as a lighting & glowing effect, to create a more cinematic movie-like look, as well as to compensate for the PS2's lack of anti-aliasing. Ico, released in 2001, then used it to create a more artistic, atmospheric look.
Bloom was later popularized within the computer game development community in 2004, when an article on the technique was published by the authors of Tron 2.0. Bloom lighting has since been used in many games, modifications, and game engines, such as Quake Live, Cube 2: Sauerbraten, and the Spring game engine.
The effect is popular in current generation games, and is used heavily in PC, Xbox 360 and PS3 games, as well as GameCube and Wii releases such as The Legend of Zelda: Twilight Princess and Metroid Prime 2: Echoes, and PS2 games such as Dark Cloud 2 and Shadow of the Colossus. The use of bloom in Fallout 3 and Syndicate (2012) are particularly notorious.