During the day we don’t see
lights that might be turned on inside a building because the daylight
is comparatively too bright. After the sun has set and the light
begins to fall off there is a period – sometimes as short
as 10 mins when there is still some light in the sky and on the
subject but the artificial lights have an effect in out image.
In this image the light has just been turned on for the clock - and we see the yellow glow of the tungsten light juxtaposed against the falling dusk light in the sky.