Definition:
In the theater, the lighting designer is a distinct, credited creative role responsible for the complete lighting concept of a production. In film, that function is performed by the gaffer working under the creative direction of the DP. The title means different things in different contexts, and the distinction matters.
What It Means in Movies:
On most film productions, the DP is the creative author of the lighting, and the gaffer executes and often co-develops it. The term "lighting designer" rarely appears as a standalone film credit because the lighting is considered part of cinematography, not a separate discipline.
Why It Matters:
The confusion between these two contexts matters because it affects how productions are structured and how creative credit is assigned. On large-scale productions captured for both live audiences and cameras simultaneously, a dedicated lighting designer may be brought in to collaborate with the DP.
Example:
On a large-scale live concert film, a dedicated lighting designer creates a lighting system for the venue and the live audience. The DP then works within that system, adapting it for the camera. The two collaborate on every setup where the live lighting and the camera requirements conflict, which is often.