Valve said they were going to redo some of the maps in HL2 with HDR lighting. They said there were a few reasons they weren't going to add HDR to the entire game though;Are Valve going to be intergrating the technology in Lost Coast (HDR and better shadows) into the rest of HL2, or even Aftermath or CS: Source?
1. The game was designed without HDR in mind, and so they think a lot of the areas work better as they are.
2. The download size for the update would be gigs in size if all the maps were redone.