My favorite time of day to photograph cities is the blue hour. Now, the blue hour really isn’t an hour at all, but a much shorter span of time that occurs before sunrise or after sunset.
In the morning, it is the transition time where the sun is inching closer to the horizon and the sky turns from inky black to an electric blue; with the opposite occurring in the evening. Depending on cloud cover, this lighting scenario happens approximately twenty to thirty minutes before sunrise or after sunset.
During this window of time, the ambient light balances with the artificial lights of buildings and monuments in urban scenes and you can easily capture the entire dynamic range of the scene. No need to take multiple exposures and stitch together an HDR (high-dynamic range) shot!
To capture the electric blue sky, it is optimal to use a tripod which will allow you to shoot with a lower ISO such as 400 or 800 and a wider depth of field like f/11 while keeping steady at slow shutter speeds. Because slow shutter speeds can easily be achieved at this time of day, I also love to play with motion blur from vehicles and other moving objects to add interest to my compositions.
But if you are tripod averse, as I often am, the solution is simple: turn up your ISO, shoot at your shallowest aperture, and do your best to reduce camera shake by bracing yourself or your camera against something solid. You won’t get to play with motion blur, but you’ll capture this vibrant time of day nonetheless.
I have to admit that I prefer photographing the blue hour after sunset rather than before sunrise. This is simply because I can easily scout out the scene I want to capture in the daylight instead of having to scout the day prior or finding myself fumbling around in the dark with a flashlight and hoping I’ve found a good position.
Once in position, take test shots and get ready for the light to change quickly. I like to take test shots and check my histogram as I go to not only adjust exposure but to also see when the scene is getting more similar in tone. I find that the optimal time for the best photograph is actually when the scene is looking a bit too dark to my eyes.