VIRTUAL PRODUCTION ROUND TABLE INDUS TRY.
HAMILL: The current developments in Unreal Engine are helping to produce more authentic photorealistic environments, and will be increasingly intrinsic to the characteristics of camera sensors and lenses. How important is an LED panel’s pixel pitch to the camera’s optics? PILBOROUGH-SKINNER: Choosing the correct pixel pitch for your LED volume is essential to negate visual artefacting and the moiré effect. Depending on the size of your volume and the required viewing distance, the tightness of the pixel pitch can vary. HUNT: There are so many variables to consider. The choice of pixel pitch depends on the shots you’re looking to achieve, depth-of-field and countless other factors. The sweet spot of mid-2mm pixel pitch works for a lot of scenarios, but there are plenty of times when having a finer, sub-2mm pitch gives advantages. Such as shooting subjects closer to the screen, which can also reduce screen size and therefore cost. We own large quantities of 1.5mm, 2.3mm, 2.8mm and 3.4mm, which all get good use for in-camera pixels – it really depends on the project’s requirements. KAESTNER: I would say that every virtual production project currently in development is a prototype of some form. The technology is evolving rapidly and fulfilling ever-higher visual demands. Each project is unique, and there is no ‘standard’ per se for a virtual production methodology. Therefore, every project will have to look very carefully at the combination of LED panels, camera chips, lenses and colour pipeline. The pixel pitch of an LED panel is one aspect that has a massive influence on the visibility of moiré or pixel patterns, when seen at certain distances, through specific lenses and camera chips. For the Netflix series 1899 , DOP Nik Summerer had special anamorphic lenses crafted by Arri, to not only create a unique visual for the show, but also complement the virtual production. Using the Alexa Mini LF in the Dark Bay volume in Babelsberg, limited the amount of moiré and pixel patterns for the distances we needed to shoot our scenes.
volume – which is harder to change. It’s a matter of taste, budget, etc. But it is most important to test your products of choice together intensively, and synchronise your camera and LED panels to get the best results. HAMILL: The pixel pitch of LED panels is critical in creating a high-resolution, realistic virtual background that is suitable for in-camera VFX. Aside from the camera optics (focal length, sensor size, resolution), there are a series of other elements (size of LED volume and distance from camera to LED screen) which all need to be considered to mitigate issues like pixelation and moiré. In theory, the finer the pixel pitch, the higher the definition. For reference, the pixel pitch of the Roe Visual Diamond panels that form the LED volume at our studios is 2.6mm. Whereas, on The Mandalorian , they used 2.8mm – but in both cases, excellent cinematic visual outputs were delivered. Does the choice you make in volume size and form (single LED wall versus volume) impact the interactive/emitted light? If so, how do you decide? PILBOROUGH-SKINNER: Most LED volumes will provide about 80% of fill light, but we always recommend physical fixtures for key lights – and some fill, depending on the scenario. For example, sunlight is almost impossible to replicate with just an LED; you can’t get the hard, direct shadows. So, the size and form of your stage should be informed by budget, the space in which you’re building the wall, and what rigging options there are for additional lighting. HUNT: An enclosed volume will certainly give a more realistic lighting environment, but that’s not to say you
HOCHMAN: This is quite critical, and the pitch depends heavily on the type of stage that is set up, along with the DP’s choice of shooting. A large volume with a 30m diameter is fine with a 2mm, since the camera distance is quite far to the LEDs – and depth-of-field works in your favour. But, on the other hand, we are seeing certain VFX supervisors prefer as high resolution as 0.9mm, so the LED screen can be extremely close to the camera without moiré. And it’s not just pixel pitch, but also the quality of the pixel itself – that’s why we actually created our own LED chemistry to make Rec. 2020 colour with exceptional viewing angles and black levels. You’ll see more of this next year. LEVY: It is a crucial topic, and the choices are determined by the size of the LED walls relative to the talent performance area, camera position, sensor size and lens choice. PRAK: It’s important in relation to the type of content you’re shooting and the kind of result you require. Anything close-up requires a finer pixel pitch, whereas wide shots work perfectly with a larger one. At the moment, most LED volumes work with anything between 2.3 and 2.8mm. For closer in, a finer pixel pitch might be preferable – like a 1.5mm. It’s good to keep in mind that this choice has two sides: the camera optics – which might be easier to change – and the LED panel used in the wall or
“The pixel pitch of an LED panel is one aspect that has a massive influence on the visibility of moiré or pixel patterns, when seen at certain distances”
35. JANUARY 2022
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