The EBU has warned that the post-production color correction costs required for video shot under LED lighting could outweigh the power savings compared with traditional tungsten lights.

This is a setback for the LED movement, which thought it had cast tungsten lighting into history as a result of not just of the greatly reduced energy consumption but also other advantages, notably lower maintenance and heat production.

Enthusiasm for studio LEDs
With LED technology, about 80 percent of the electrical energy is converted into light, compared with 20 percent or less for tungsten bulbs, which emit most of the rest as heat or infra red radiation.

The issue, though, has been in matching LEDs to the well-known light profile of tungsten bulbs, which the industry had thought it had solved. In the U.K., the BBC has been experimenting with LED lighting for production for more than three decades, and has recently used it on the sets of popular shows such as the hospital drama "Casualty." The BBC says it has developed tests that assess the color rendition of low energy light sources, and has stated it wants to send a clear message to the broadcasting community and to its viewers about the leading role that LEDs play in sustainable low energy production helping meet targets for reduced carbon emissions.

There has been similar enthusiasm for studio LEDs elsewhere, and they have been used in the U.S. for filming popular prime-time reality TV competitions such as "Dancing with the Stars," "America's Got Talent" and "American Idol."

Premature to embrace LEDs fully in the studio
But now the EBU suggests it may be premature to embrace LEDs fully in the studio, even if they are now ready for the home. Problems that have been identified include inconsistencies between factory batches, insufficient brightness and inability to spotlight subjects, especially from a great distance. A further issue is that color LED lights are prone to color shifts and inconsistencies that can be especially evident when lighting people's faces.

The EBU is not suggesting broadcasters should avoid LEDs, but urges them to recognize that many new LED lights fail to perform as well as had been expected or promised. The EBU has come up with its own recommendation to help broadcasters assess how well their television lighting performs. Called R 137, and accompanied by a software-based analysis tool, this is designed to quantify how well a set of test colors is reproduced when illuminated under a given light and viewed through a standardized camera and TV system. The software compares the differences in colors produced by the light source under test with those rendered under standard lighting conditions. It assigns a value from 0 to 100 to each light tested, and that value gives an indication of how much color correction would be required to produce acceptable results with that light.

In addition to the value assigned to the light, the software also provides additional information that can be used to advise colorists on how much correction is needed. In cases where the value assigned to a light is less than 50, the results may still be unacceptable, even given a lot of correction.

This procedure is likely to be only required for a temporary period while the LED lighting industry continues to improve and refine its products. LED lighting will indeed be ready for prime-time production, but as so often with emerging technologies, not quite as soon as everybody hoped or manufactures led us to believe.

Source from: http://broadcastengineering.com