Valve"s latest Steam news update bangs on once again about Half-Life 2: The Lost Coast, which aims to showcase the sort of high-end graphical techniques that we can expect from future Valve titles - including High Dynamic Range lighting.
This time, however, it also features an interesting little video, which you can download by clicking on a thumbnail on the news update page, that allows you to see how regular high-end Half-Life 2 lighting compares to a build using HDR - splitting the image down the middle and showing vanilla on the left and HDR on the right.