Some night-time subjects, such as buildings, are too vast to be illuminated with a flashgun or even numerous coupled flashguns. However it is possible to photograph such subjects in a totally different manner. One technique known as "painting with light" can not only be used to illuminate progressively a large or relatively distant subject but can also be used in endless creative ways. Two basic approaches are commonly used. One relies on open flash and the other on the use of some other convenient source of light such as a powerful flashlight.
Set up a camera on a very stable tripod and frame the picture as required using a relatively wide-angle lens so that the camera-to-subject distance is not too great. Set the lens aperture to f/11 or f/16 and the shutter release to the "B" setting. Set a flashgun to manual operation and the correct film speed, and ensure that it is equipped with fresh batteries. It is also worth having a spare set of batteries handy. Then take a meter reading from the sky to ensure that the required shutter speed will be long enough to walk around the subject - typically a few minutes.
When everything is ready, note the shutter speed and the time on your watch, and set off at a brisk pace to walk a planned route around the building during which the flashgun is fired, using the test button, as many times as necessary to illuminate the required areas. Having two flashguns, used alternately, can be helpful because it is then not necessary to waste the recycling time. In general it is wise to dress in dark clothing and keep moving relatively quickly. This eliminates any possibility of the photographer appearing in the image.
Keep an eye on your watch, try to avoid exposing the same area with more than one flash and, when sufficient flashes have been made, return to the camera and close the shutter after a period as close as possible to the predicted exposure time. Also remember that, when using film, reciprocity failure will affect the chosen exposure. The exposure period should be increased to compensate for this effect.
The second method is very similar but relies upon a flashlight to progressively illuminate the scene. Project the beam of a torch onto the building from a known distance and take a meter reading from the illuminated area. Then set a suitable aperture, perhaps f/16, and calculate how long each area of the subject must be illuminated from a known distance for correct exposure - say three seconds from a distance of five metres. It is then just a matter of locking open the camera's shutter, using the "B" setting, and walking a planned route around the building whilst illuminating the required areas for the necessary periods of time. Areas that are wanted brighter can be illuminated from a shorter distance, or for a longer period, and those required to be less well lit can be passed over more quickly or from a greater distance. Large buildings may require extended periods of time to achieve proper illumination. An exposure of ten minutes might be required. In such cases, take a light measurement from the sky to ensure that the ambient light is sufficiently low to allow the long exposure.
These techniques can also be used creatively to illuminate selected parts of a scene, or even a person within the frame. Results are inevitably a little unpredictable so it is always worth repeating the process a few times. Be willing to experiment and learn by experience.