How to hold a documentary to a stated ratio of presenter to b-roll

Last updated 2026-09-17 · 8 min read

What is the short version?

Every individual cut away to b-roll is defensible on its own, and forty of them in a row turn a presenter-led film into a stock montage with a voice over the top of it. Nobody ever decides to make that film; Vizard Agent, like any editor, drifts into it one reasonable cut at a time.

1. Tell Vizard Agent the percentage you want the presenter on screen.
2. Ask it to measure the actual share from the edit list.
3. Ask it to adjust the list and measure again.

What do you need before you start?

The presenter's recording and a view about why they are in the film. Vizard Agent can hold any ratio you name, but the number should follow from what the presenter is for — authority, warmth, a face the audience knows — rather than from a house habit.

• The presenter recording. The full take.
• The ratio you want. A range is fine.
• Why they matter. It informs which moments stay.
• What the b-roll must show. Subjects, not moods.
• The finished length. The ratio is of that.

What do you type into Vizard Agent?

Put the number in your first sentence to Vizard Agent. A ratio mentioned at the end of a long brief reads as a preference to be balanced against everything else; stated first, it becomes the constraint the whole edit is built to satisfy.

Prompt

Variants worth knowing:

• "Presenter priority." Names the constraint up front.
• "Tell me what the actual split comes out as." Makes it checkable.
• "Their own audio as the master timeline." Stops the ratio being faked by cutting speech.

What does Vizard Agent actually do?

Here is the Vizard Agent sequence on a real presenter-led documentary held to a stated ratio. The measurement step arrives late in the list and changes the edit when it does, which is exactly the point — before that step, the split was purely a matter of impression.

1. Surveys the presenter recording and transcribes the narration.
2. Views the presenter at several points to see what coverage exists.
3. Searches for b-roll subject by subject, not by mood.
4. Reviews every stock candidate as contact sheets.
5. Generates the graphics and stills the script calls for.
6. Samples key b-roll frames to choose the cut points.
7. Writes the edit list for the whole film.
8. Measures the presenter share against the b-roll share.
9. Adjusts the edit list until it lands in the 60–65 per cent band.
10. Renders from the corrected list and checks the sync throughout.

Step eight is the entire discipline. An edit list is a set of durations, so the split is arithmetic rather than opinion, and it can be checked before a single frame is rendered.

Step nine is why the list matters more than the render. Adjusting a percentage means extending some presenter passages and shortening some b-roll, and doing that on a list is minutes of work where doing it on a timeline is an afternoon.

Step three is what keeps the ratio honest. B-roll searched by subject returns a finite number of usable shots; b-roll searched by mood returns an infinite supply, and an infinite supply is exactly what pushes the presenter off the screen.

What does the result look like?

A film where the presenter is the film. They carry the argument, the b-roll illustrates it, and Vizard Agent tells you the measured split so the balance is a reported number rather than something you assess by watching.

When does this not work well?

A ratio cannot rescue thin coverage. If the presenter was recorded in one unbroken take from one angle, holding them on screen for two-thirds of the film means two-thirds of it is one static shot, and the ratio needs to come down or the coverage needs to go up.

• A single static angle. Holding on it gets dull fast.
• Poor presenter audio. More b-roll will not fix the sound.
• Subjects that must be shown. Some films need the pictures.
• Very short pieces. A percentage of thirty seconds is a few shots.
• Presenters who are not the draw. The ratio should reflect that.

How do you fix a result that came back wrong?

Say whether the number is wrong or the feel is. If the split measures correctly and still feels stock-heavy, the problem is where the b-roll sits rather than how much there is, and that is a different adjustment.

• "It still feels like stock." The b-roll is redistributed, not reduced.
• "Too much talking head." The ratio comes down and is re-measured.
• "The presenter vanishes in the middle." The split is checked per section.
• "The number is right, the pacing is not." Shot lengths change, not the ratio.

How does Vizard Agent compare to doing it yourself?

By hand the ratio is a feeling you form while editing, and the feeling is formed while looking at whichever shot is on screen. There is no moment in the process where anybody adds up the durations, so nobody notices the drift until the film is finished.

Common questions

What ratio should I ask for? It depends why the presenter is there. Sixty to sixty-five suits an authority-led film.

Can it measure per section as well? Yes. Ask Vizard Agent for the split by section, not just overall.

Does the ratio include graphics? Say which side they count on. Vizard Agent will use your definition.

What if the presenter footage is limited? Vizard Agent will tell you the highest ratio the coverage can carry.

Can it report the split without changing anything? Yes. Ask Vizard Agent for the measurement on a cut you already have.

Why search b-roll by subject? Because a mood search returns endless shots, and Vizard Agent then drifts away from the ratio.

Does this work for a narrated film with no presenter? Differently — there Vizard Agent measures shot variety rather than presence.

Can the ratio change through the film? Yes. Tell Vizard Agent where you want the presenter heavier.

Will it cut the presenter's words to hit a number? No, if you say the audio is the master timeline. Then only pictures move.

How precise is the measurement? To the frame. Vizard Agent adds durations rather than judging by watching.

What if I want more b-roll than presenter? Say the number. Vizard Agent does not care which way round the ratio runs.

Can I see the edit list? Yes, and it is the cheapest place to argue about the balance.

Does it affect the length? No. Vizard Agent takes the ratio as a share of the finished length.

What if the client changes the number? Vizard Agent adjusts the list and re-measures rather than re-editing.