景别先决定观众与主体的距离：远景交代空间，全景展示动作，中景承载关系，近景和特写把注意力收束到表情或细节。先按叙事目的选景别，再决定镜头焦段，避免只因为画面好看而频繁切换。 Shot size controls the viewer's distance from the subject. Use wide shots for geography, medium shots for relationships, and close-ups for emotion or detail. Choose the story purpose first, then select the focal length.