Virtual production opens up amazing new possibilities for a DP, but as with any new technology there are certain tips and tricks to getting the best out of it.
Virtual production technically covers a number of things, but what people normally mean by it is shooting on an LED volume. This is a stage where the walls are giant LED screens displaying real-time backgrounds for photographing the talent in front of. The background may be a simple 2D plate shot from a moving vehicle, for a scene inside a car, or a more elaborate set of plates shot with a 360° rig.
The most advanced set-ups do not use filmed backgrounds at all, but instead use 3D virtual environments rendered in real time by a gaming engine like Unreal. A motion-tracking system monitors the position of the camera within the volume and ensures that the proper perspective and parallax is displayed on the screens. Furthermore, the screens are bright enough that they provide most or all of the illumination needed on the talent in a very realistic way.
Over the last year I’ve been fortunate enough to speak to several cinematographers who have worked with this exciting new technology, and I’ve gleaned the following tips.
1. Shoot large format
To prevent a moiré effect from the LED pixels, the screens need to be out of focus. Choosing an LF camera, with their shallower depth of field, makes this easier to accomplish. The Alexa Mini LF seems to be a popular choice, but the Sony VENICE (and possibly VENICE 2) evidently works well too.
2. Keep your distance
To maintain the illusion, neither the talent nor the camera should get too close to the screens. A rule of thumb is that the minimum distance in metres should be no less than the pixel pitch of the screens. (The pixel pitch is the distance in millimetres between the centre of one pixel and the centre of the next.) So for a screen of 2.3mm pixel pitch, keep everything at least 2.3m away.
3. Tie it all together
Several DPs have found that the real foreground and the virtual background fit together more seamlessly if haze or a diffusion filter are used. This makes sense because both soften the image, blending light from nearby elements of the frame together. Other in-camera effects like rain (if the screens are rated weatherproof) and lens flares would also help.
4. Surround yourself
The most convincing LED volumes have screens surrounding the talent, perhaps 270° worth. Although typically only one of these screens will be of a high enough resolution to shoot towards, the others are important because they shed interactive light on the talent, making them really seem like they’re in the correct environment. Pioneering DPs report that a ceiling screen is incredibly beneficial for producing a naturalistic “sky” light.
5. Match the lighting
If you need to supplement the light, use a colour meter to measure the ambience coming from the screens, then dial that temperature into an LED fixture. If you don’t have a colour meter you should conduct tests beforehand, as what matches to the eye may not necessarily match on camera. Some volumes now have LED lights hooked up to their servers so that they can be fed pixel-mapped data matching the on-screen images.
6. Avoid fast camera moves
It takes a huge amount of processing power to render a virtual background in real time, so there will always be a lag. The Mandalorian works around this by shooting in a very classical style (which fits the Star Wars universe perfectly), with dolly moves and jibs rather than a lot of handheld shots. The faster the camera moves, the more the delay in the background will be noticeable. For the same reason, high frame rates are not recommended, but as processing power increases these restrictions will undoubtedly fall away.