The key light is the first and usually most important light that a
photographer,
cinematographer, or other scene composer will use in a lighting setup. The purpose of the key light is to highlight the form and dimension of the
subject. The key light is not a rigid requirement; omitting the key light can result in a
silhouette effect. Many key lights may be placed in a scene to illuminate a moving subject at opportune moments.
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LUCE CHIAVE [CINEMA]. ILLUMINAZIONE SUL PIANO PRINCIPALE [CINEMA]