PJ: Now that CMOS sensors are creeping toward a million ISO, digital photography is able to capture night images that we couldn't even imagine before.
Still, a mechanical camera can take eight-hour exposures, even in sub-zero weather. This is useful to record long-term transitions within a scene.
The moon and stars become arcs of light, bodies of water look like sheets of ice and a crowded plaza becomes a de-populated mist.
These visual aspects of long exposures complement the hard-edge linearity of the architecture and industry in my current series.
If it's windy, or even breezy, don't bother with analog night photography. Always using a tripod, I don't touch the camera while the lens is open. Even a cable-release transmits too much hand-vibration for critical detail. Instead, I block the light with an eight-inch card covered with black velvet. I open the lens, let the camera vibrations settle down and simply lift the card up and down for an exposure. Exactly like they did before shutters were introduced in the 1800's.
If there's time, it's best to set up before dusk and photograph the progression into full night. You want to catch the few minutes when the artificial light balances with the fading sunset to retain detail in the shadows.
Cities are not always that dark, especially when they're soft-lit by a glowing low-cloud canopy. Nevertheless, most nocturnal light levels don't even register on meters and film sensitivity drops off with longer exposures, so I estimate the luminance, based on previous sessions, and take a series of exposures, bracketing them in one-stop increments.
A typical set of exposures of an urban night scene might be 5 seconds through 8 minutes at f16, using Ilford Delta 100 film. So that would be: 5s,10s, 20s, 40s,1m, 2m, 4m and 8m. I finish the twelve-frame roll with best-guess exposures. Slightly over-exposed negs scan better than underexposed ones.
When staying at a hotel, I'll ask for a room with an upper-floor balcony, then check out the conditions for an extra-long urban night shot.
When it's gotten truly dark, I set the aperture at F 22–32, open the lens and set the iPhone's alarm for 6-8 hours; before the first light. When nothing goes wrong, there's been some surprisingly good results, especially in under-lit in cities.