Since the beginning of this gaming generation companies have been discusses the size of levels, and spurred debates about the necessity of the capacity of Blu-ray.
Before the release of the launch title Resistance: Fall of Man, Insomniac was talking about how large each level of the game was. According to the Ratchet & Clank developer, each level took up to 300MB, and the whole game summed to 17GB of a single layer Blu-ray disc.
Now it has been revealed that the one Killzone 2 level shown at the pre-E3 event last night weighed in at roughly 2GB. Guerrilla Games has stated on numerous occasions that it intends to fully utilise the PS3's capabilities, and clearly it will be using Blu-ray's capacity for Killzone.