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LED FUTURE LIGHTING
Definition: Should lighting companies look to adhere to a colour standard for LED lighting now that CRI levels are very similar and consistent? Al DeMayo, co-founder/CEO, LiteGear: Yes. For cinema and television use, standards (actually recommendations) already exist such as Rec. 709, Rec. 2020, and several others. Digital cameras – and their ability to adjust white-balance with plus and minus green cast and optional low-pass filters – make the white point a moving target. White light output from any manufacturer should be able to fall exactly on the Planckian Curve with near-zero Delta UV (the distance and direction of colour shift from the Planckian locus), meaning the light is neither too green or too magenta. Coloured light should be provided only within the gamut of the chosen colour space such as Rec. 709. I think it is our best chance at achieving inter-vendor operability. Byron Brown, product manager, Litepanels: The best colour standard for LED lighting is the full colour, 360° spectrum. Most colour standards, like CRI, select a few common colours and measure how well a LED light renders those colours. The best LED lights will render a full and level spectrum for all colours and offer highly flexible and precise colour adjustment. These lights will also perform well on colour standards like CRI and TLCI since those standards are a small subset of the full spectrum. Dedo Weigert, Dedo Weigert Film: Yes, it is true that recently the CRI levels of LED light sources have gone up and are now in the higher 90s. At the same time, we have to be reminded that CRI is a system from 1931, which include
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ADHERING TO A STANDARD DEPENDS ON HAVING A STANDARD
my mind, and as far as I know, refers mainly to studio cameras with three CCD sensors; and even those were not all reacting in exactly the same way. Klaus Hamlescher, product support, Sumolight: An advantage of the CQS for gaffers is the fact that all colour values are combined through a root mean square average so a LED with low single colour values gets a lower overall rating. The average for the CRI is calculated so that a LED can have weak single colours like the important ones for skin tones (R9, R13, R15) and still have a very high rating, which is not ideal. As all colours with CQS are evaluated in its saturated maximum this helps owners of shops to understand their lighting quality requirements but is less useful for digital camera cinematography and post-production. As long as all CRI values are displayed and taken into account separately we are happy with the traditional colour rendering index. Frieder Hochheim, founder, Kino Flo: Adhering to a standard depends on having a standard. CRI is a photopic standard (your eye) and bears little relevance to the spectral response curves of cameras. Since lighting manufacturers all have different levels of technical expertise you will always have a range of product quality; quality in colorimetry, software features, design and construction. Establishing
only eight pastel colours, and it totally misses out on the important red and skin tones (R9 and R13). So if we talk about CRI, we must talk about expanded CRI; but even by those standards LEDs have become a lot better. But then there are other ways to look at it. CRI is based on the response of the human eye, therefore, if you are talking about museum lighting and about people watching the artwork, CRI may indeed have some significance. TLCI by Alan Roberts I think is a great step forward and goes much deeper into it, but in
BELOW Why are there so few LED options for high- output directional sources? Read on.
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AUGUST 2018 DEFINITION
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