Vectorscope

What is a vectorscope?

A vectorscope ignores where a pixel sits in the frame and how bright it is. It keeps two values per pixel: hue and saturation. Each pixel becomes a dot on a round graticule. The center is zero saturation, so white, grey and black land in the middle; the further a dot sits from the center, the more saturated it is, and its direction names the hue.

Six target boxes mark the colors of standard color bars: red near 11 o'clock, magenta near 1, blue near 3–4, cyan near 5, green near 7, yellow near 9. Opposites face each other across the center, which makes the scope a working picture of color theory: a trace leaning orange is pulled back with teal-blue.

A grey room with one actor makes a small central blob with a short arm toward the skin hue; a neon street throws long arms toward magenta, cyan and blue. It is a basic tool of color work, built into grading apps and many on-set monitors.

How to read a vectorscope

1. Where is the center of the trace? Find something that should be neutral: a white shirt, a grey wall, a chart. If the image is balanced, it sits on the crosshair. Shifted toward blue, the shot has a blue color cast; toward yellow-orange, it is too warm.

2. Which way do the arms point? Each arm is a dominant hue. Arms toward orange and cyan mean a complementary colors look; one long green arm means a scene washed in green.

3. How far do the arms reach? Length is color saturation. A muted drama keeps the trace compact; arms far past the 100% targets usually mean the signal is out of gamut for delivery.

There is no brightness axis: a lighter and a darker color with the same hue and chroma land on the same spot.

Where is the skin tone line on a vectorscope?

Most vectorscopes draw a line from the center toward the upper left, between the red and yellow targets, at roughly 11 o'clock: the skin tone line, also called the flesh line or I-line. Skin of every complexion has nearly the same hue and differs mainly in brightness and saturation, so on a balanced image a face makes an arm along that line.

Window the face so only skin feeds the scope. An arm swinging toward magenta means pink, sunburned faces; toward yellow-green, sickly ones. Fix the overall balance first, then rotate skin back with a hue control. A deliberate green night look pulls skin off the line on purpose; the point is to know it.

Why DPs and colorists rely on it

Eyes adapt: after ten minutes in a grading suite a warm image reads as neutral. The scope does not adapt, so it is the fixed reference in the room.

• Balancing shots. Before any look, the colorist centers the neutrals of every shot.
• Matching cameras. Shooting one chart with every body shows which camera leans magenta or green, even with identical white balance settings.
• Building a look on purpose. A teal-and-orange grade, like the orange desert against teal sky in Mad Max: Fury Road (2015), shows up as two opposite arms. If skin drifts off its line while the background goes teal, the colorist sees it at once.
• Staying legal. Saturated reds and blues break delivery limits first; the scope shows them before QC does.

On set, a DP checks a grey card in the key light the way a false color mode confirms exposure: trust the measurement, not the monitor.

How to use it in a grade

1. Balance first. Turn on the skin tone line, find a neutral and use offset or lift-gamma-gain until it sits on the crosshair.
2. Check skin. Window the face; its arm should lie on the line.
3. Build the look. Push the palette and watch the trace move. Stop when the look reads, not when the arms touch the edge.
4. Match the scene. Compare two shots: shapes differ with framing, but the center and skin arm should agree.
5. Check limits. Pull back arms beyond the targets, especially red and blue, with a saturation curve or gamut limiter.

Vectorscope vs. waveform monitor

A waveform shows brightness: it plots the image column by column, black at the bottom and white at the top, for exposure and contrast. A vectorscope shows only hue and saturation, with no brightness or position. Use the vectorscope for neutrals, skin and saturation, the waveform or RGB parade for blacks, highlights and contrast.

Models have no scope, but their frames can be read on one: drop a generation into your grading app and the vectorscope shows whether the model tinted everything or pushed skin orange. Fix it in the prompt by naming a neutral object, the white balance and each light's color. Keep scope screenshots beside the takes on one FlashBoards board.

Common mistakes

• Warm skin by default. Cinematic or golden pushes faces orange. Name the white balance and ask for natural skin.
• A tint over everything. Say which surfaces are warm and which are cool.
• No neutral to check. Put a grey card, white shirt or grey wall in frame.
• Fake scopes. Models invent graticules; measure real frames in your grading app.

Further reading

Alexis Van Hurkman, Color Correction Handbook: Professional Techniques for Video and Cinema. Charles Poynton, Digital Video and HD: Algorithms and Interfaces.