Shooting for VFX: what to capture on the day

A visual effect is two worlds sharing one frame: the world you photographed and the one we add to it. Ours has to obey yours in light, lens and movement, or the audience feels the join. The shoot day is the only day your world can be measured. At wrap the set is struck, the sun moves on, and every unanswered question becomes guesswork in post.

We live on the receiving end of shoot days, matching plates on shows like The Chosen and Testament.

The short version lives on our Learn page: eight cards, ninety seconds of habits. This is the why behind them: what each habit buys, and what it quietly costs when skipped.

Ninety seconds on set becomes days in post

On the day, reality does the work for free. In post, an artist rebuilds it by hand.

Camera data is the plainest example. To add anything to a moving shot we first rebuild your camera in 3D: same lens, same height, same move. With the focal length and a couple of measurements logged, that solve is quick and certain. Without them, an artist reverse-engineers it from pixel drift, and the guesses show up as a shot that slips and swims. Thirty seconds with a slate, or hours of detective work per shot.

Clean plates are the same trade in a different costume. After the take, clear frame and roll ten seconds of empty set. Now anything that has to be removed, a rig, a cable, a reflection of the crew, gets patched with the real background, which matches perfectly: same place, same light. Without one, a painter invents that background frame by frame. The removal happens either way. One version takes minutes. The other takes days, times every shot that needed one.

What the grey ball actually tells us

Every crew has watched someone hold two balls on a stick in front of the lens and wondered why. They're light meters for post.

The grey ball shows how light behaves on a known surface: where it comes from, how hard or soft it falls, what colour it really is after the set has bounced it around. The chrome ball is a mirror of everything: every lamp, window and bounce card in a single frame. An HDRI goes further: a panorama of the set that keeps the true brightness of every source. We light CG with your actual set, not our recollection of it.

It's the difference between CG that belongs in the frame and CG that sits on top of it. An audience can't name a wrong shadow or a highlight that's too cool, but they feel it, and the note comes back as "it doesn't look real". With reference, that note mostly never arrives. The pass takes about a minute. It might be the highest-value minute on the call sheet.

Where greenscreens and markers go wrong

Most greenscreen trouble is one mistake: the actors are too close to the screen. Green bounces onto shoulders and hair, and when the green is keyed out, the person's edges go with it. The fix in post is roto, tracing people by hand, frame by frame. The fix on set is walking the cast a few metres forward.

Evenness is the other half. A screen with hot patches and shadows isn't one green, it's a dozen, and each needs its own key. Light it flat and even, no wrinkles, no footprints if the floor is in shot. A clean screen keys cleanly. A patchy one is keyed patch by patch.

Markers are the judgement call. They exist to give tracking something to grip where a surface offers nothing: flat green, bare walls, smooth floors. On textured surfaces they're clutter: the texture already tracks, and every marker has to be painted out of every frame it appears in. So: markers where nothing else can be tracked, nowhere else. Keep the spacing consistent and tell post what it is: that's how we recover the true scale of your set.

The calm crew

None of this is difficult. All of it is skippable, and on a hard day everything skippable gets skipped unless somebody owns it.

The productions whose post goes smoothly aren't the lucky ones. They're the ones where data capture is a habit with a name attached: one person who logs the camera, rolls the clean plate and runs the ball pass as routinely as the slate. Done that way it costs nothing; nobody breaks stride. Treated as an afterthought, it becomes a negotiation about time on the one day there's no time to negotiate.

The same habit decides the bigger calls. A two-minute call to your VFX team before improvising a new shot usually ends in a cheaper way to shoot it. If a shot might be extended or stabilised, frame a little looser: post can crop in, but it can't invent what the lens never saw. Real smoke or fire, photographed safely, arrives already matching. It's why Testament's fire was shot for real, not simulated.

The crew that captures data calmly is the crew whose post goes calmly. Calm in both places comes from the same decision: someone worked out, before the pressure arrived, whose job it is to notice.

If nobody owns those ninety seconds yet, that's the gap on-set supervision fills, and a planning session before the day is the place to settle it.