How to match exposure and white balance across shots by measuring skin tone
Ask Vizard Agent to measure the skin tone and the black level of every shot before grading anything. Those two numbers are what "matching" actually means, and they let white balance be fitted per camera and exposure per shot — which are different problems that a single eyeball adjustment tries to solve at once.
What is the short version?
Shots from two cameras, or from one camera across a day, do not agree. Grading them by eye fails in a specific way: your eye adapts to whichever shot is on screen, so each one looks correct while you are working on it.
- Ask Vizard Agent to measure skin tone and black level per shot.
- Ask for white balance fitted per camera, exposure per shot.
- Say the warmth must survive the brightness fix.
What do you need before you start?
The shots, and a view about which one of them is right. Vizard Agent fits everything towards a single target, and that target ought to be a shot you actually like the look of rather than a mathematical average of a dozen shots you do not.
- Every shot. Including the ones you might cut.
- A reference shot. The one others should match.
- Which camera is which. Balance is fitted per camera.
- The look you want. Neutral, or warm.
- Any shot that must not change. A hero shot, usually.
What do you type into Vizard Agent?
Name the two measurements to Vizard Agent. Asking simply for the shots to be matched invites one overall grade across everything; asking for the skin tone and the black levels to be measured turns the same job into a fit against numbers.
Prompt
Variants worth knowing:
- "Measure the skin tone and the black level." The two anchors.
- "Balance per camera, exposure per shot." The right division.
- "Keep the natural warmth." Protects the thing a fit will flatten.
What does Vizard Agent actually do?
Here is the Vizard Agent sequence on a real multi-shot film graded to match across two cameras. The refit at step eight is the interesting one: the first fit corrected absolutely everything, including the natural warmth that was supposed to stay.
- Measures the exposure and colour of every shot.
- Measures the skin tone and black levels shot by shot.
- Fits a matching grade for each shot against the reference.
- Fits white balance per camera rather than per shot.
- Fits exposure per shot on top of that.
- Renders the graded shots for review.
- Judges the matched grade on real frames.
- Refits exposure only, keeping the natural warmth.
- Fits one exposure per take at a brighter target.
- Renders the corrected grade and rebuilds the film.
Step four is the division that makes this tractable. A camera has one white balance for the whole shoot; exposure changes shot to shot as the light does — so fitting them together makes each correction fight the other.
Step two explains why skin is the anchor. Everybody knows what skin looks like, so a shot where it is slightly green reads as wrong even when nothing else does, and a measured skin tone is something shots can be fitted towards.
Step eight is the correction worth expecting. A fit that matches everything perfectly will also remove the warmth you liked, so the second pass adjusts brightness alone and leaves the colour where it was.
What does the result look like?
Shots that cut together without anybody noticing the cameras. Skin reads the same across the film, blacks sit at the same level, the warmth survives, and Vizard Agent gives you the per-shot measurements so the grade is a set of numbers rather than an opinion.
When does this not work well?
Measurement needs something to measure. A shot with nobody in it has no skin tone, a shot lit by a coloured source is meant to be that colour, and footage that is clipped has no detail to recover in the first place.
- Shots with no people. No skin to anchor on.
- Deliberately coloured light. A neon scene should stay neon.
- Clipped highlights. Nothing to bring back.
- Very different formats. Log and standard footage need converting first.
- Heavy compression. The measurements get noisy.
How do you fix a result that came back wrong?
Say which shot it is, and which of the two variables you think is wrong in it. "Too dark" and "too cold" lead Vizard Agent to two entirely different fits, and it can adjust either one of them on its own without disturbing the other in the slightest.
- "Shot four is too dark." Its exposure is refitted; colour untouched.
- "It has lost the warmth." Exposure only is refitted, balance restored.
- "Camera B still looks green." The per-camera balance is re-measured.
- "They match but look flat." The target moves; the fit is redone against it.
How does Vizard Agent compare to doing it yourself?
By hand you grade shot one, then shot two to match your memory of shot one, then shot three to match your memory of shot two. Errors accumulate in one direction, and by the tenth shot the film has quietly drifted somewhere nobody chose.
| By hand | Vizard Agent | |
|---|---|---|
| Matching | Against memory | Against measured numbers |
| Drift | Accumulates down the reel | Every shot fitted to one target |
| Balance and exposure | Adjusted together | Fitted separately |
| Warmth | Lost to the correction | Protected in a second pass |
| The record | A set of adjustments | A set of measurements |
Common questions
Why skin tone? Because viewers know what it should look like. Vizard Agent anchors the fit on it.
What about shots with no people? Vizard Agent uses the black level and whatever neutral reference the shot contains.
Why fit balance per camera? Because a camera's balance does not change between shots; the light does.
Can I pick the reference shot? Yes, and you should. Otherwise Vizard Agent fits towards an average.
Will it flatten my look? Only if you let it. Say the warmth stays and Vizard Agent refits exposure alone.
What if a shot is clipped? Nothing can be recovered there. Vizard Agent will tell you which ones.
Does it work on log footage? Yes, once converted. Vizard Agent handles the conversion first.
Can it show me the numbers? Yes, per shot. That is the useful output as much as the render.
What about a deliberately coloured scene? Exclude it. Tell Vizard Agent which shots are meant to be that colour.
How many shots can it fit? As many as the film has. Each is measured separately.
Will the black levels match? Yes. They are half of what Vizard Agent measures in the first place.
Can it match to an existing film? Yes, if you give Vizard Agent a reference frame from it.
Does this replace a grade? No. It makes the shots agree; the look is a separate decision.
What if only one shot is wrong? Then Vizard Agent refits only that one and leaves the rest exactly as they are.