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How to pull focus on subjects displayed on the LED wall | Virtual Cinematography

How do you focus on something that is not there, but is seen “in” the LED wall, something like an animated digital character, that’s inside the LED virtual set?

Pulling focus to objects and subjects that are displayed on an LED wall.

Virtual Production Training / Director of Virtual Production Asa Bailey.

You want to pull focus from the cast on-set to the fully virtual character that’s being displayed on the LED wall. The problem, if you role your optical focal point forward from position A to position B with the on-set camera, as you roll to and then through the actual front of an LED wall, you’ll end up hitting the moiré zone. Moiré is a French word meaning “having a wavy or ripply surface pattern” and it is what we call the effect when the on-set camera focus, hits the LED wall and creates a mess of lines and artifacts in your shot. Not good. So how do you shoot around this and pull focus to subjects inside the LED virtual set?

On-Set Facilities train crews to user virtual production methods and technologies.

We take a look at one of the methods I’ve developed for pulling virtual focus, one that cuts the focal move of the optical camera, just short of the LED and the moiré zone, meanwhile, the in-engine virtual camera continues to pull the focus move, to position the virtual cameras focus point on the target subject in the virtual world.

By stopping the optical camera short of the wall, you miss the moiré zone, instead, what you get is the optical camera, to it’s sharpest point, looking at a frame of the LED, but stopping short without hitting the LED wall and dreaded moiré zone. What the optical camera frames up on, the LED, will still be out of focus, but that’s until the virtual camera completes it’s move, sharpening up the image in the LED, in effect, also sharpening up the images that the optical camera is looking at too. You just pulled focus to a virtual object.

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This coordinated focus pull maneuver takes time to set up and master, but once a crew is practiced in the method, it does become more intuitive and more of a dance between the on-set camera operator and the engine virtual camera operator, as they maintain and follow each others lead, to create the illusion of focus. You don’t need any special hardware or equipment to pull this move, a simple focus wheel on the on-set camera, and someone in the engine ready to slide the virtual cameras focus. You may want to get some hardware input wheels and sliders to better control the in-engine focus, Monogram are good, and we’ve tested them, very easy to set up.

Asa Bailey
Director of Virtual Production

 

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