Television Lighting Consistency Index
The Television Lighting Consistency Index (TLCI) is a key figure for evaluating light spectra and light quality. In addition to the known color rendering index (CRI or Ra) with respect to eight reference colors and Re with enhanced reference colors, the TLCI a more intensive evaluation of the spectral composition of light. The EBU ( European Broadcasting Union , Eng. European Broadcasting Union ) as a technical committee for The film industry developed this index in 2012 under the exact name TLCI-2012 and recommended it under the title R137 ( Television Lighting Consistency Index - 2012 and Television Luminaire Matching Factor - 2013 ).
history
With the introduction and increased use of LED technology in the theater, television and film industry, it has been shown that the color rendering index Ra, which has been used since 1960, is no longer sufficient to adequately assess the required light. Today the lighting in the studios is increasingly measured by using spectrophotometers in TLCI. This recommendation was developed within the EBU between 1970 and 1980 by the "LED Lights Project Group" within an EBU strategy program and was updated with R137.A 2012.
Calculation method
To measure the TLCI, precisely those color locations are used which are also relevant for recording and display on television technology devices (cameras, displays). Using a spectrophotometer, the industry now offers a large number of portable devices that examine the light spectrum for 24 color locations in the color diagram and use an algorithm to calculate the index, which ranges from 0 to 100.
Presentation of the measurement results
The measurement results are shown graphically in the form of a color table (see Colorchecker ). In addition, the color values are shown in direct comparison with the reference values. Percentages indicate a measure of the deviation.
In addition to the color table, the measurement method according to TLCI-2012 also calculates the correction values as a recommendation for the colorist, cameraman or photographer for subsequent comparison during digital image and video processing.
Evaluation of the measured values
| TLCI | meaning |
|---|---|
| 85 to 100 | The color errors are minor; no correction of the color values is required. |
| 75 to 85 | The producer will probably make corrections to the color setting. The result is just about acceptable. |
| 50 to 75 | The producer will almost certainly need to make color corrections to get an acceptable result. The time required is considerable. |
| 25 to 50 | The color rendering is poor. Improvisation with compromises is necessary for correction. However, the TV requirements cannot be fully met. |
| 0 to 25 | The color reproduction is almost unusable. Color corrections are hardly possible anymore. |