What is the rule that maintains the left and right relationship of a subject so that they do not appear to be flipped by the viewer?

The 180-degree rule is a vital guideline in filmmaking and cinematography that helps maintain spatial relationships between characters and objects in a scene. It dictates that an imaginary line, or axis, should be established between two subjects, and the camera should remain on one side of this line during a scene. This prevents the viewer from becoming confused about the positions of the characters or objects, ensuring that left and right relationships remain consistent throughout the sequence.

When filmmakers adhere to this rule, they uphold the continuity and clarity of the scene, allowing the audience to easily follow the action without disorientation. If the camera crosses this imaginary line, it can cause characters to appear flipped in relation to one another, which may disrupt the viewer's immersion and understanding of the scene's geography.

Other concepts like the rule of thirds focus on composition rather than spatial relationships between elements. The principle of continuity involves various techniques to maintain consistency, but it doesn’t specifically address the left-right orientation of subjects. Eyeline match deals with how characters look at one another and the perspective the audience perceives, but again, it does not directly manage the left and right spatial relationship as the 180-degree rule does.