File:Postprocess controller local contrast.jpg

The final technique used in Left 4 Dead was local contrast. This is a technique borrowed from photo retouching, where the contrast is adjusted specifically on areas of an image that contain a high level of visual detail. This technique helped make the visuals sharper and more focused. This ended up being great shorthand for us, as it effectively imitated the feeling of an adrenaline rush or near-death experience. The effect gives the player a sense of heightened perspective, and was a great subliminal way to let them know a zombie attack was coming.