In the first part of the season 3 finale of Buffy: The Vampire Slayer, a flashback shows an interaction between Angel and Drusilla in a church confessional. In the background outside the confessional, there is a clearly displayed cross. One could reasonably assume that there are many other crosses/crucifixes displayed throughout the church.
- The Master was not afraid of the sight of a large cross, but was burned when he touched it.
- Angel is not visibly affected by the sight of the cross necklace he gives Buffy, but it does burn him.
- When Spike is talking to Buffy, he is not visibly affected by the cross around her neck.
So the vast amount of evidence points to the sight of a cross/crucifix not having a negative effect, but physical contact causing burning. But then again:
Angel is shown being warded off by the sight of a cross after he has lost his soul.
So how exactly do crosses/crucifixes work?