It is generally true to say that the more that is happening in a shot, the less continuity matters. But in a constrained, intimate situation, every head turn counts.
Two characters are having a quiet tête–à–tête over dinner. They are eating, and sometimes talking, but nothing much is happening visually. In such a situation it is most important to be accurate about all the actions, even head nods and slight gestures, particularly where the director has planned to cover the scene with complementary two shots. In these shots both characters are in vision all the time and it is only possible to cut from one to the other when the dialogue and action match exactly on each shot.
If the director has planned a coverage of single shots on each person, the action is not so critical as most of it is out of view. The props also are of great importance in such a scene.
The opposite extreme to an intimate situation in terms of observing detail for continuity would be a fight sequence, including a large number of people as well as a great many props. It would be impossible to notice everything, especially head nods, in a situation with such violent activity. But in this kind of set-up you should note carefully what the principal actors are doing and try to keep track of their relationship with other groups.
For instance, in the early part of a scene two principals may be fighting with each other. They are surrounded by supporting artists. In the latter part of the same scene the principals are still fighting it out, but the supporting artists have cleared save for a group on camera right. So remember that.
Also, be aware of clothes becoming disarranged during a fight and possible make-up requirements, like blood and bruising, that may have continuity with other shots and scenes.
1. In a scene with little action, every detail of continuity is important.
These two complementary two-shots will only cut together if continuity matches exactly in every detail.
2. But in a scene with a lot of action, accuracy over every detail is not so vital.
Just pay attention to the principal characters and have a general idea what else is happening in the shot.
