Arsh Broadcast

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همکاری NVIDIA و ARM

With around one and a half years to go until the Tokyo Olympics, Japanese broadcaster NHK is readying for what will inevitably be a watershed point for 8K. But the cameras that will be used, internally at least, be unlike any outside broadcast camera ever used for such an event before. Phil Rhodes looks at current sensor technology and asks what this means for such broadcasts.

Between now and the Tokyo Olympics in 2020, NHK should have put the finishing touches on its plans to broadcast the games in 8K. Going by their regular exhibitions of “super hi-vision” at various trade shows, they’re already well on the way, with cameras, displays, and even ways to send the pictures over radio links to and from remote areas. Sports broadcasting is one of those few places in which delivering 8K pictures to the home might actually make sense: keen sports viewers report that a sufficiently high-res picture on a sufficiently large screen replicates being in the stadium quite well and without the inconvenience and indignity of a VR headset.
 At the same time, it’s become ever easier to shoot resolutions well beyond 4K for the big screen, and by that, we mean theatrical release, given that 8K home TVs had better be pretty big screens as well. In the world of feature film and high-end drama production, though, there’s often less intention to send all eight of those Ks from the camera to distribution. Usually, people shoot high-res for drama because it’s useful in modern post-intensive approaches to production. Even straightforward scenes, without visual effects, can be subject to cropping, stabilisation and replacements of inconvenient corporate insignia or anachronistic details in a period piece, and that can be done better – if not more easily – with more pixels to play with.

The problem is that the increasing ease and convenience of extra-high resolution in drama production is not really reflected in broadcast production. The same could, at one time, be said for 4K: early 4K broadcasts were sometimes done with cameras such as the F65, outfitted – perhaps slightly awkwardly – for live-to-air production work. Sensor technology has improved since and both Sony and other manufacturers have produced 4K broadcast cameras which behave in much the same way that studio cameras always have. It keeps the crew happy – but to date, it’s been difficult to do that for 8K.

Putting large numbers of pixels on a sensor means the pixels have to be small, which in turn means less light will hit them. That means turning up the sensitivity, risking noise and potentially compromising the clarity and sharpness that we’re aiming for in the first place. It is, frankly, beyond 2018 technology to make an 8K sensor the size of those in most broadcast cameras – which are well under half the dimensions of a 35mm film frame – with acceptable performance.

Yes, cell phone cameras are tiny and have almost supernaturally good apparent performance, but that can be very heavily reliant on mathematical post-processing that isn’t reliable enough for broadcast work. Given improvements in computing, particularly artificial intelligence, that might change. For now, though, a truly professional camera needs a sensor that can do good work without massaging the pictures into shape after the fact.

Because of this, 8K broadcast cameras generally have much bigger sensors than traditional types. Often, they’re the size of an APS stills frame, as with Sharp’s 8C-B60A camcorder. It’s a powerful camera, with an 8K sensor and high-quality onboard recording. Even so, its sensor is roughly the same size as a 35mm movie frame. That’s potentially fine, but it does mean that traditional broadcast lenses from the likes of Fujinon and Canon don’t usually cast a large enough image to cover the whole sensor. Lenses that do cover larger sensors get us back to a way of working that’s much more like drama or feature film and not ideal for the fast-paced pressure of a live sports broadcast. It works, but to experienced live production crews, it’s far from ideal.

Sony’s solution is the UHC-8300, which spreads the load across three monochrome imaging sensors. Each of them is intended to see the red, green or blue channel, just like a conventional broadcast camera. That means a colour splitter block, of course, with a prism and filters, which is complex and expensive, and means that lens design is also complex and more expensive. The UHC-8300 does work with conventional broadcast lenses which are designed with all this in mind, but it still uses larger-than-usual imaging sensors to keep performance high. As a result, the image needs to be optically enlarged, which makes it dimmer, so the camera is effectively less sensitive than its small-chip cousins.