I photograph a lot at twilight at the end of the day. It is arguably my favorite time for photographing. The other time of day that I love photographing is in the early morning light. Though most photographers talk about afternoon light as their favorite, I am not one of them. I like the afternoon light as much as the next photographer, but twilight and early morning, those are the best.
The ideal twilight photograph has magical color in the sky, usually, blue or purple though sometime it can be orange too. This sky usually plays off of an equally compelling element of neon lights, street-lamps, campfires or other light sources, typically in the foreground of an image. The interplay between those two light sources and their respective two color palettes is often what makes a great twilight photograph. The art of twilight photography is getting all of those elements together at just the right time and at just the right exposure.
Most photographers know how swiftly fleeting that time window is, when the sky is just right and the exposure for both the sky and the light source are about the same. Photographing earlier than this exact moment yields an image with the correct sky exposure but the lights will be too dark. An image made much later, with a good exposure only for the lights, will have nice lights but the sky will be solid black. Knowing exactly when to photograph at twilight is definitely a learned skill. Over the years of doing twilight work I have figured out a couple guides that have helped me and will help any photographer.
Usually during the twilight at the end of the day, by the time the sky looks good it is too late. That means that the smart photographer starts to photograph the twilight scene with the great sky and great lights earlier than what seems right, just when the sky appears a bit too light. If that same photographer continues to photograph the twilight through the time when the sky goes darker then black, he or she will note, upon reviewing their images, that the photos made earliest in the process, before the sky looked “best” to the naked eye, those are the ones that appear best as photographs.
The other guide I use is what I call the first and second twilight. We all know the sun sets in the West and that is where the twilight magic I am describing actually happens. But if you look to the East (as the sun sets in the West), you will see that Eastern sky going through an abbreviated version of the twilight first, evolving from blue to purple to black. The first twilight, the one to the East, is similar to the second one that you will see a few minutes later in the Western sky.
Knowing that you have two twilights to work with can vastly improve your photography if you plan accordingly. By that I mean you can use the first twilight to think about your exposure and “practice.” For example, in Missoula, Montana there is bar with a fabulous neon sign that I have photographed a few times. The bar sits on a nearly perfect North-South axis so the neon sign can be photographed against both the first and the second twilight. This is a great way to “practice” the shot with the first twilight and master the final image during the second twilight.