When Ingmar and I made 'Winter Light', which takes place in a church on a winter day in Sweden, we decided we should not see any shadow in it at all because there would be no logical shadow in that setting. I said, 'Oh, that will be an easy picture for me because the light doesn't change in three hours'. Ingmar said, 'That's what you think. Let's go to the churches in the north of Sweden'. And there we sat for weeks, looking at the light during the three hours between eleven and two o'clock. We saw that it changed a lot, and it helped him in writing the script because he always writes the moods.

Shooting With Ingmar Bergman
A conversation with Sven Nykvist at the American Film Institute 1984