Overview

In lighting terminology, rendering refers to the color reproduction of a light source – how faithfully it renders the colors of illuminated objects compared to a reference light source of the same color temperature. A lamp with poor rendering distorts colors (typical for sources with a discontinuous spectrum, such as some LEDs or discharge lamps), while a source with good reproduction accurately displays skin tones, costumes, and set decorations.

On set, color rendering is a key selection criterion for lighting fixtures because poor color reproduction is only partially correctable in post-production – if a color range is missing from the spectrum, the camera cannot record it.

Metrics: CRI and TLCI

Color rendering is quantified using indices. The two relevant for film and TV are:

• CRI / Ra (Color Rendering Index): The general color rendering index Ra is the average of eight test color samples (R1–R8). The scale is typically 0–100, where 100 represents the reference source. Values from approximately 90 are considered good. The CRI evaluates the color perception of the human eye, not that of a camera.
• R9 (saturated red): An additional color sample outside the Ra average. R9 is particularly important for the reproduction of skin tones and is therefore often specified separately in film practice.
• TLCI (Television Lighting Consistency Index): Specifically developed for TV/film; it evaluates color rendering as a camera sensor "sees" it, rather than through the human eye. Scale 0–100.

Rating Levels (CRI vs. TLCI)

On-Set Usage

When selecting LED fixtures, lighting technicians and DPs look for high CRI and, especially, TLCI values so that light sources from different manufacturers match in color within the frame and the correction effort in post remains low. For TV and broadcast productions, the TLCI is considered more indicative than the CRI because it accounts for the spectral sensitivity of the camera. The TLCI was developed by Alan Roberts (formerly BBC) together with the European Broadcasting Union (EBU); the calculation is specified in EBU Tech 3355 as "TLCI-2012".

Note – Distinction of Terms: "Rendering" in the sense of Color Rendering should not be confused with the rendering in CGI/VFX and post-production (the calculation of images from 3D scenes) or with image "rendering" in editing software. In lighting technology and equipment datasheets, rendering refers to color reproduction.