We spent a few days in London on our way to safari in Zambia and Botswana over the past few weeks, and I did the totally tourist things ... rode the double-decker bus, went to London Tower, walked around Piccadilly, etc. Actually, it is a great city, and a lot of fun to be photographing something other than fish and divers.
Mostly I walked around with my Canon G11 and took snapshots of the landmarks and my family. But, at least one night I went out semi-seriously to shoot nightscapes (these with my Canon 5DMKII), in particular the Parliment buildings and Big Ben over the Thames. The issue was to try to hold detail in the bright areas (like the clock tower) and also by able to bring out the darker areas like the reflections in the water. It seemed a natural candidate for the high dynamic range tool in the new Adobe Photoshop CS5.
The short story on HDR is that it combines a number of exposures, automatically in software, to extract the best of the highlights and shadows and composite in a single image.
Here are the four exposures I used to make the HDR image, each a full stop apart in terms of shutter speed:
Here is the image that Photoshop CS5 created for me:
Very impressive new technology, and this tool plus the content aware functionality are reason enough to upgrade to CS5.