I was waiting at the airport for Deborah to return from a trip. There's construction at the airport, so the passenger exit is mostly blocked until people come through the doorway.
From where I was sitting I could see the shadows of the passengers moments before they walked out the door. I tried to identify Deborah by her shadow before I saw her. It is hard to tell someone's height from their moving shadow, but I was looking for short hair. I also knew she had a rolling suitcase.
The moment between the shadow and when someone emerges was so brief and fleeting that as soon as I saw what turned out to be her shadow, I saw her before I could even determine that it was her shadow.