The Source engine periodically gets a revamp. The last time was in late 2007 when Orange Box came out. At that time, coinciding with the release of Ep2 and Portal they did the "2007" update which actually back-ported HDR into HL2. Originally Lost Coast intro'd it and Ep 1 was the first release with it OOTB. Play HL2 in the last 4 years, though, and you'll see HDR is now in.
I was expecting a major jump for Portal 2, but instead it was another minor one. Not too much change from Portal 1 to 2. They're still DX9-only, which is another interesting thing as their own hardware surveys indicate a significant minority of their audience has DX10/11 capability between video card and OS.
The Jedi Master
