What I See- Casablanca

So for my film 101 class, we spoke about Casablanca. I had never seen it before so I decided to watch it. I loved it. I noticed how the character played by Ingrid Bergman (Ilsa) always seemed to have the "halo" lighting or back light. It gave her a very angelic look. The lighting on her seemed to be different from all the other actors. She was always lit with high key lighting, low contrast of shadows. There was a specific scene, when she goes to see Rick (played by Humphrey Bogart), that she looks completely innocent and angel like. She has a close up where we could see a small portion of her shoulders and she is wearing a cloth over her head. She seems to glow in this shot.
During the scene where Rick is drinking, before the flashback, there was low key lighting. Rick's face had a shadow over half of his fast which gave me the idea that something was wrong. The whole scene was shot with low key lighting until Isla comes in and she is shot with high key lighting. Although the flashback and the lighting on Rick gave me the sense that he was in pain and he felt betrayed by her, the lighting on Ilsa did not give me the sense that she was the type of person to betray Rick and that there was more to her reasons for not leaving with him.