LIGHTING SPECIAL COLORIMETRY
PIXEL PERFECT Assimilate’s Live FX creates live composites for every manner of virtual production deployments
with a colour space,” Aderhold explains. “We support all the colour spaces and transfer functions of every manufacturer, and all the standardised ones. That’s a pure technical conversion that doesn’t include tone mapping. It’ll be technically correct, but won’t look great out of the box. To make it look the way the DOP wants, Live FX ships with all the colour grading tools in the world.” Similar things are possible for Image- Based Lighting, with the software capable of understanding the behaviour of individual lighting devices. Both Miller and Aderhold concur on the idea that lighting might soon begin to implement the same sort of colour standards used in video. It’s been particularly relevant to Assimilate’s work, as Aderhold reflects: “We’ve been doing video for the last 20 years, and went into the lighting business... now all our video stuff is being requested for lighting purposes.” Standardising communications, then, has never been more necessary – and given the huge range of ways in which lighting devices are built, it’s essential that lighting manufacturers observe standards, since it isn’t practical for control applications to assume full external control of the hardware. “When you get into lights which have amber, lime and cyan LEDs in them, we can’t possibly do the mathematics to go from RGB to RGBACL because we have no idea about the electronics in all those fixtures,” Aderhold states. “We send RGB data to the fixture and the manufacturer
takes this and does the mathematics to control the amber, cyan and lime light emitters from that. The image content we’re playing back to a wall or a light is all RGB-based anyway, and you have to calculate a white, a cyan, an amber and a lime colour from that at some point in the pipeline. But the light manufacturer knows best how to do that.” In practical circumstances, gaffers may prefer an approach based on hue, saturation and value, which separates brightness from colour so that the overall brightness of the light can be controlled independently. This is, Aderhold says, still a work progress. “We’re not yet 100% sure precisely what is expected. Many fixtures have a dedicated dimmer channel to make them brighter or darker. We also have the RGB gains and a master gain… if I have RGB data and I dial down the master gain, it probably doesn’t just get darker, it might also appear more or less saturated – that’s what we need to separate from each other.” For now, software like Live FX seems likely to remain the answer, for the simple reason that it provides such a rich toolset. “You get the tools from post for live virtual production,” Aderhold continues. “You can dial in a sunset look or do crazy stuff like a sky replacement – if the director doesn’t like the sky, you can go ahead and put in a new one. Or key certain colours, desaturate just the reds because they pop too much, or make a particular colour pop a little more because it should.”
The result will be a blurring of concerns which were once distinct. It might also mean more computer horsepower on- set in order to handle real-time video effects. “It just depends on what you are doing,” Aderhold suggests. “A primary grade – colder, warmer, whatever – that’s background noise to the GPU even at higher resolutions. As soon as you key something and want to blur your key, you really need something beefy. “It’s where the industry is moving towards,” Aderhold concludes. “The difference between video walls and lighting starts to blur massively, and that’s not only in the way you drive those things, but also in the nomenclature. Gaffers are now asking to colour manage their lighting set-up – they want to use their own RGB matrices or load 3D LUTs onto fixtures. It turns out all our video stuff is becoming more and more relevant in the lighting world.” YOU CAN EVEN DIAL IN a sunset look, OR CRAZY STUFF LIKE sky replacement ”
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