What is TLCI? Understanding the Television Lighting Consistency Index

A common challenge when choosing a light source is finding one that accurately shows the colors around you. To offer the highest level of color rendition, an artificial light source must precisely recreate the spectral wavelengths of natural light. Some color rendering measurements, like CRI, measure light quality based on the perception of the human eye. However, in film and broadcast applications, the ways in which color can be distorted through camera components must be considered. TLCI aims to provide an accurate measurement for these scenarios.

The TLCI, or Television Lighting Consistency Index, measures how accurately film and television cameras interpret colors under an artificial light source. Measured on a scale from 1 to 100, a higher rating indicates a near-perfect color fidelity and minimal color correction needed. This index was developed to help broadcasters and film color correctors assess lighting equipment intended for film and broadcast use.

To understand why TLCI is so valuable, we must first understand the contrasting ways in which the human eye and camera sensors “see” color. The human eye perceives color by detecting light wavelengths through photoreceptors in the retina, which convert these wavelengths into signals that the brain interprets as specific colors. Camera sensors, on the other hand, use a series of sensors and filters that detect color and translate it into digital signals that are processed into the display. The response curves between the human eye and a camera show the results of these differences.

To measure TLCI, advanced software models the data processing of various industry cameras into an average response, creating what we consider the “standard camera.” This standard camera then observes an X-Rite ColorChecker card (previously the Macbeth ColorChecker chart) showing 24 specific colors formulated for color rendering tests. The first row features skin tones and natural colors, the second and third rows include a range of saturated colors, and the last row displays a grayscale. The greyscale, however, is primarily used for checking lighting balance in the studio and less for color rendering. 

The ColorChecker card is observed under a reference light and the test light. A different reference light is used based on the color temperature of the test light: lights with a CCT less than 3400K use a Planckian black body, lights with a CCT over 5000K use natural daylight, and lights with a CCT between the two use a mixed illuminant. After being viewed under the reference and test light, the colorimetric differences for each color sample are calculated, and the average between values determines the overall TLCI rating.

The data below shows the results of a TLCI test for one of our high TLCI LED strip lights. You can see the scores for each individual color swatch. The bottom-most score on the chart indicates the total TLCI rating for these strip lights: 99. Data from the report shown below can be extremely helpful for color correctors by indicating which color ranges likely need the most correction work during post-production.

TLCI values can be broken down into the following levels based on the necessary color correction during post-production. Color correction is the process of adjusting the colors in an image or video to counteract imbalances and improve the overall quality of the captured footage.

• 85-100: No color correction needed; anything over 90 is considered “television-ready”
• 75-85: Minimal color correction needed, can easily achieve an acceptable result
• 50-75: Color correction necessary, but could become acceptable for broadcast
• 25-50: Below broadcast standard, significant time needed for color correction
• 0-25: Terrible color quality, unusable for broadcast

The Color Rendering Index (CRI) is a well-known metric used for determining the color rendering quality of a light. However, in a film and broadcast setting, CRI fails to account for how light is perceived through camera equipment. CRI measures a light source's ability to reveal the true colors of various objects compared to a natural light source based on the perception of the human eye. This makes CRI important for certain retail and commercial settings where accurate in-person color rendering is essential, but not the preferred measurement for film and broadcast applications.

Measuring CRI slightly differs from measuring TLCI. In a CRI test, a “standard observer” is used in place of a standard camera. Only 8 color samples from the RA system are used, and the samples cover a smaller range of colors, excluding dark skin tones and natural colors that are commonly present in film footage.

Our new line of high TLCI LED light strips has a near-perfect TLCI rating of 99 and a high CRI of 98, ensuring they are ready for film, TV, and photography use. Their peel-and-stick 3M™ adhesive backing allows for fast, easy mounting around a variety of surfaces. These lights utilize energy-efficient LED technology, allowing you to leave your lighting on for long periods of time without worrying about high operating costs. Install these strips in professional-grade photography, video, or television studios and enjoy high-quality light for years to come.