Resuming a shoot after a break

You film the first half in the morning, break for lunch, come back and film the rest. In the edit the two halves refuse to go together. The light has gone warmer, your fringe has moved, and the camera is looking at you from very slightly further left than it was.

None of that was visible in the room. All of it is obvious on a cut, because a cut puts two moments side by side and invites a comparison nobody makes while filming. So photograph the setup before you stop, and compare against it when you return.

Why does a break show up on a cut?

The eye is not measuring anything. It is registering difference at a boundary.

Two frames a second apart, one warm and one cool, read as an error to somebody who could not tell you what changed. What they feel is that something is wrong, and it lands on the video rather than on the light. A film set has somebody whose whole job is this. You have a camera on a tripod and a sandwich going cold.

What to photograph before you walk away

Three photographs on your phone, taken before you stop.

One from behind the camera, showing the whole frame including the background. One of yourself, arms down, from the front. One of the room from the side, showing where the camera and the light stand in relation to you.

That is fifteen seconds of work, and it converts every check below from memory into comparison. Leave the tripod alone, and if the floor allows, tape under each leg and under your chair.

What has moved while you were gone?

A cooking partner's pre-shoot list led with exactly this. Five things move while you are away, and not one of them announces itself.

The light

The sun, mostly. If any part of your light comes through a window, its direction and its colour have both moved while you ate, far enough over a couple of hours to see. Either close the curtain and work on artificial light so the room stops depending on the weather, or accept the shift and structure the video so the halves never touch.

Check too whether a lamp has come on somewhere: a hallway light somebody flicked on their way past is now part of your setup.

You

Hair is the usual offender, the front more than the back. Compare against the photograph rather than the mirror, because the camera sees you the other way round from how you see yourself.

Then clothing. A jumper taken off after lunch creates a continuity change you may need to hide, separate into chapters or make deliberate. Check glasses, sleeves and jewellery too.

The camera

Nudged by a knee, or the tripod head has crept downwards under the weight, which is what they do. Compare the frame against the photograph before anything else.

Then check the camera has not made decisions for you. Some return to automatic exposure and automatic white balance when switched off and on. White balance is the camera's decision about what counts as white in the room, which sets how warm or cool everything else looks, so a camera that has quietly reassessed it hands you two halves in two colours.

The levels

Level is the recording volume: how loudly the microphone writes into the file. If the dial moved, or the recorder came back at its default, the second half is a different loudness.

Reclip the microphone in the same place, on the same layer of clothing and at the same distance from your mouth. A few centimetres can change tone as well as level; matching placement is easier than repairing a mismatch later.

The room behind you

A chair has moved. A cup has appeared. A door that was shut is open, with a corridor behind your head. You stop seeing the background; the viewer looks at it throughout.

Why do you miss it at the time?

Because your eyes are doing you a favour.

Vision adapts as the colour of the light changes, so a shift can become less noticeable while you are in the room. A camera on fixed white balance keeps its setting; automatic white balance can introduce a different change between takes.

The rest is attention. While filming you are watching whether you said the words right, not whether the plant behind you has moved, which is the argument for a checklist rather than for concentrating harder.

What if the two halves already do not match?

Some of it comes back and some does not.

Colour comes back up to a point: a grade pulls the second half towards the first, and the further apart they started, the more the fix shows. Framing comes back within limits, by punching in, which is a digital zoom and costs a little sharpness. Loudness comes back easily; tone does not.

Wardrobe and hair are usually better handled by restructuring than by attempting a digital repair. Keep the halves apart, lay b-roll across the seam or make the break deliberate with a title card.

Five minutes that decide the edit

There is a version where you never bother, because you have filmed in the same room a hundred times and nothing has ever moved. Then one afternoon the window is open, the light is bouncing off a white van outside, and you find out six weeks later with a deadline.

Take the photographs. They are the only part of this that still works on the day you forget to do everything else.

Sources and evidence

What here is established colour science, and what is our own before-and-after check.

What is established. The CIE's daylight locus documents that daylight's chromaticity shifts along a defined path over the course of a day, from a cooler overcast sky to a warmer low sun, the colour-science basis for two clips filmed an hour apart disagreeing about colour even though nothing in the room itself was touched. CIE colorimetry more broadly underpins treating white as a setting a camera has to be told rather than something it senses on its own, which is why an automatic white balance can quietly reassess it between takes.

Our method. Photographing the frame, the person and the room before stopping for a break, and comparing against that photograph rather than memory, is this studio's own check, not a claim that every viewer consciously notices what moved.

References.

• Rinner, O. & Gegenfurtner, K. R. Time course of chromatic adaptation for colour appearance and discrimination. pubmed.ncbi.nlm.nih.gov. Chromatic adaptation has a slow phase (half-life about 20s) with the white point still shifting out to about 120s. Adaptation is not complete 'within a minute'; most of it is, full adaptation runs to about two minutes.
• Fairchild, M. D. & Reniff, L. Time course of chromatic adaptation for colour-appearance judgments. pubmed.ncbi.nlm.nih.gov. Two-component adaptation: fast (about 1s) and slow (half-life about 30s), about 50% complete after 1s. Substantial adaptation continues past 60s; not full within a minute.