20th March 2015
How good is your LED light for its intended use?
How can you tell if an LED light is good enough for use in the fields of cinematography, broadcast and professional video? How can you tell if a light gives an even amount of light across the visible parts of the spectrum, without giving your image a colour bias? The answer might be to rely on TLCI.
Television Lighting Consistency Index (TLCI-2012) applies a mathematically calculated figure, ranging from 0 to 100, to a measurement of the spectral power distribution of a luminaire. A Spectroradiometer is used to make the measurement. This new standard, invented by ex-BBC colour science expert Alan Roberts, is recommended by the European Broadcast Union (EBU). The closer the figure is to 100, the better it is. A figure below 85 may require a colourist to correct the images recorded.
The more familiar CRI measurement was invented several decades ago for architectural lighting. Most Tungsten Halogen fixtures used in film and television scored 100 or very close to it. However, the CRI standard proved inadequate when applied to LED fixtures. TLCI is proving to be a more relevant measurement for us, although still not accepted as an international standard. Most LED manufacturers are more than willing to have an independent evaluation using TLCI. Alan Roberts has published his findings to date on the Guild of Television Cameramen's (GTC) website.
To support Alan's work, Prokit has carried out some more Spectroradiometer readings recently, and calculated their TLCI measurement. Here are the results:
Model Setting Qa
BB&S Area 48 Softlight Daylight 98
Lowel Pro Power LED Daylight 94
Zylight F8 Daylight Daylight 94
Spark Lighting SL-2424B Tungsten 97
Spark Lighting SL-2424B Daylight 95
Spark Lighting SL-2424B 4300K 96