Twilight: Break it Down
Chasing perfect light.
When photographing interiors, the quality and intensity of sunlight, outside, is important, but is rather permissive. You'll likely want to shoot during the day (because dark windows would be odd, unless you have something specific in mind) and perhaps avoid direct sunlight blasting through (unless slivers of light are what you are going for). I tend to prefer overcast days (or working on the side of the building receiving indirect light) when shooting interiors, since they provide me with very soft light washing in through the windows.
Exteriors, on the other hand, are far more uncompromising: the quality, direction, color and intensity of the light, as well as the weather, can make or break the shot (not to mention the season, the cars parked in front of the building, and a long list of other imponderables). This requires planning (you'll want to study where and when sunlight hits, considering the side of the building you want to shoot) and some luck, otherwise you're unlikely to get a successful result.
Consider, for example, the shot below, taken late in the day, while the sun is approaching the horizon:
The direct sunlight is falling on the building (as opposed to backlighting the building) and the weather is nice, which is a start. Moreover, it's got more character than flat midday light, I suppose, yet it remains very harsh white light with deep shadows. It simply isn't working.
Twilight, to my eye, usually provides the most gorgeous light. The idea is to shoot just before sunrise, or just after sunset (when no direct light hits the building, since the sun is below the horizon), at precisely the sweet spot when the artificial light and the ambient light are matched to perfection. A few minutes too soon or a few minutes too late and one will overpower the other, ruining the shot.
The multiple (increasingly longer, from 2 seconds to 30 seconds) exposures below, taken just a few minutes apart, demonstrate clearly how quickly light is changing at sunset. The final shot (shown at the beginning of the post) was taken at 7:11 PM, when the artificial light and the ambient light were balanced just right.
Finding the "sweet spot" with multiple exposures.
In the end, the exposures were in the order of 15-30 seconds (at ƒ/11), which was tricky as I had my tripod set on a step ladder to get a slightly elevated point of view. By 7:19 PM, the interior lights were nuclear, it was already too late. This means that the window of great light was no longer than about five minutes!
Notice how the light in the apartment on the left, second floor, is darker. I ended up compositing a longer exposure of this window in the final shot for it to balance properly with the other windows. Also notice how, at the last minute, the neighbor got in his office and turned on a light (you can't plan for something like this!), a window I also composited in the final shot.
The shot below was taken the day before, at the same "sweet spot" time of the sunset, but while some light rain was falling on my camera, demonstrating how the weather can profoundly affect the result:
The same "sweet spot", with an overcast sky.
Once I faked a blue sky, it was surprisingly not bad at all, but it doesn't look as "natural". Notice how much brighter the building and the ground are, because of the soft white overcast sky. This image is also a good demonstration that for a better result, you'll want basically all the interior lights to be switched on, otherwise the building will look "dead". That is why sunset often works better than sunrise, because in the morning, the interior lights are not typically turned on like we want.
Here is a "before and after" of the keeper; it is a composite of four exposures and a ridiculous amount of meticulous work to remove all the nasty electric cables and fix a number of other issues:
This beautiful building was designed by architect Guillaume Lévesque.