This option allows to minimize HDR and Bloom effects in the game, which cause the most usage of the CPU. In this way, win of the FPS may variate from 5 to 25 FPS, depending on the videocard and CPU power, and also RAM ammount.
Configuration example: Athlon 3000+ S939/ASUS HD3650 356MB GDDR3/1GB DDR
Result before: 3-15 FPS
Result after: 15-35 FPS