GEAR. COLOUR SCIENCE
Pixel peeping
output. Putting that technology in a video wall panel might let the resulting display put the principal cast in a suitably flattering light, although until that sort of technology is widespread – and probably even after that – virtual production is likely to require more conventional lighting as well. BEYOND RGB It almost seems uncharitable to refer to state-of-the-art modern LED lighting as ‘conventional’. Even common designs are often expanding beyond red, green, blue and white in their keenness to achieve high colour quality. Rosco DMG’s original light engine involves six different emitters, including a phosphor-converted red and, as the company’s Charlie Verne says, “Cameras are more pleased by the phosphor LEDs, because they tend to be out of gamut a lot less. Much of my job is speaking to gaffers and board ops… and colourists, because they’re directly influenced by what we make. Pictures for video walls can come from a variety of sources, although most will use either carefully prepared live action material – often relying on at least some compositing work – or real-time 3D rendered pictures. The latter can involve racks full of high-specification computers running something like Unreal Engine with careful synchronisation. Although, in the end, the result is the same: one or more SDI or DVI connections which need connecting to a large array of LED video wall panels. The hardware that manages the division of the signal, colour processing, calibration and other key parts of the process exists in what’s usually a rack-mounted processor, that communicates with compatible
panel’s capability to squeeze as much performance out of the panels as possible. Other proprietary tricks involve better handling of wide colour gamuts and HDR. With the bigger virtual production facilities creating displays tens of thousands of pixels across, forming a seamless, high-performance display from such a tornado of pixels is no small task.
Calibration, for instance, is naturally crucial to avoid the inevitable manufacturing variations between panels being visible as rectangles in the display. Although it can sometimes have a lowest common denominator effect of dimming the whole display to a level achievable by the least- capable emitters, Brompton’s dynamic calibration maintains enough awareness of the
hardware in each panel via fibre networking. One of the world’s most prominent suppliers of both processors and the associated panel interface cards is Brompton Technology. Its Tessera series offers features that not only solve problems, but tell us a lot about the challenges involved in getting the best out of large, expensive arrays of LED video panels.
“The engine has been in development since 2017, and we came out with the SL1 Mix in 2018,” Verne continues. “When it was released, it was fairly limited in terms of colour temperature range, and in software we’ve improved it quite a bit. For the DMG Dash, we managed to cram everything into a five-inch design.” That kind of engineering decision often involves a straightforward compromise of colorimetry and power. “You can sacrifice quality for output; you can create output with TLCI, CRI or TM30 that’s much worse – the better the colour rendering, the lower the efficiency. The best answer is found in the middle.” With all this technology, Rosco is keenly aware of its relevance to virtual production, and particularly the idea of lights with individually controllable subpixels for integration with the video display. “We’re working on profiles for virtual production,” Verne confirms. “We’d love to do some pixel lights down the road.” Meanwhile, the practicalities of
“The better the colour rendering, the lower the efficiency. The best answer is found in the middle”
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