XR Virtual Production has been gaining so much momentum this last year, and it feels like everyone is talking about it! There is seemingly no end to all the new content, and online events like Epic Games 2022 Virtual Production Week are doing an incredible job showcasing all the amazing talent and projects popping up everyday. In fact, many of our favourite new shows have started reaping the benefits virtual production has to offer, and we couldn't be more excited!
As more projects adopt virtual production workflows we are provided a glimpse at how complex these workflows can become, and, like every new technology there are going to be some hiccups we have to iron out [especially as we learn its role in filmmaking]. This seems to be true no matter how big the production gets, even the first season of Disney's The Mandalorian ran into some serious issues with their LED volume while filming using virtual production.
The challenge of virtual production is figuring out how we can integrate these incredibly powerful technologies into a filmmakers toolkit without disrupting their tried and true workflows. New innovations can revolutionize the way we create but if we're not careful productions can face unprecedented delays and simple things like moiré can quickly eat up a production budget in post-production fixes.
Moiré, also known as aliasing, is a serious problem for virtual production, and it can show up in your production in various ways. The Virtual Production Glossary identifies the problem of Moiré as “[a]n undesirable interference pattern caused by the mismatch between the sensors on a digital camera and a complex, repetitive pattern.” [x].
These visual artefacts are usually the most obvious when the pattern being captured is similarly complex or as dense as the imaging sensor capturing the footage.
This effect is something you’re actually probably familiar with, if you’ve ever tried to take a picture of your tv or computer monitor you’ve probably noticed that you can get these unintentional patterns whenever your camera is focused on the screen.
This can be a neat effect for artists if made intentional but isn’t quite as ideal in virtual production where the virtual background is supposed to blend and extend the real sets.
By the way… if you’re still asking “What IS virtual production? Don’t worry, we’ve got you covered here with an explainer on all things XR Virtual Production on LED Walls.
But what does this actually mean for an ICVFX Production on an LED Volume?
This issue becomes even more pronounced when you’re shooting XR Virtual Production, using an LED screen.
LED Volumes are built of individual LED Tiles. Each LED tile houses an array of individual LED diodes and the space between these diodes, is called the shader, and this negative space creates the harsh contrast that camera sensors struggle to focus on.
That space between the diodes [the pixel pitch] creates the complex repetitive grid pattern that your camera sensor grid conflicts with resulting in that undesirable moiré effect.
The greater the space between these diodes the greater your pixel pitch is going to be, and depending on your camera, the greater your pixel pitch is the further you have to keep your camera from the screen to avoid further interference.
Pre-production decisions now have to accommodate the possibility of unforeseen moiré ensuring that there is enough space on your LED Volume to allow for camera and depth of field adjustments.
These limitations can greatly restrict certain camera movements and can determine whether or not desired shots can be attained at all.
Fortunately, we’ve established a few easy fixes to this problem that you can use on-set to quickly find a solution without having to re-calibrate your LED Volume.
Three quick ways to solve moiré for XR virtual production:
Don’t focus on the screen - If you focus on the pixels of the screen the moiré will show into the sensor of the camera, instead keep the focus directed on the actors and foreground elements and not so much on the horizon.
Shoot at a shallow depth of field - the more depth you have in your shot the less the moiré will translate to your cameras sensors
Take a step back - if you find that your camera is still catching those patterns pull the camera further from the wall, reposition your shot, and re-evaluate and if you’re still seeing moiré in-camera don’t be afraid to take another step back.
Of course there are other ways to get around the moiré problem, some more effective than others.
For example, in The Mandalorian the choice to use anamorphic lenses was in part because viewers really resonate with the unique look they create, but these lenses provide the added bonus of disrupting the patterns that can cause moiré by distorting the pixels being projected onto the camera sensor.
This blending of pixels also gives a more believable feel to your shots by creating a look with increased focus fall-off blending the virtual and physical environments more seamlessly.