Angle and distance

Everything you have measured so far has been brightness: the waveform for the whole frame, the parade for its three channels. The key you place and the ratio you stretch are both brightness too. The parade already tells you a cast is there: one channel sits apart from the other two, and you can see roughly which channel it is on. It cannot name the color, though, or say how much of it is in the frame. The vectorscope does both, and it works like a compass.

The angle around the scope is the hue. Red, yellow and green each sit at a marked target box, and so do cyan, blue and magenta. A hue's place on the scope is fixed and readable. The distance from the middle is the saturation. The further the trace reaches out, the more chroma the frame has, which is the trade's word for the color content itself. A pure gray frame has no color to place, so its trace collapses to a dot at the center. A neon sign throws a single spike out toward the sign's own hue.

The vectorscope, with hue targets around its edge and the trace cloud near the center
Angle is hue and distance is saturation. The six boxes mark calibrated color-bar positions. They are references, not limits for ordinary pictures.

In DaVinci Resolve, open the Scopes panel on the Color page and choose Vectorscope. You can pop the scopes into their own window with Cmd-Shift-W on macOS or Ctrl-Shift-W on Windows. Keep the picture visible beside it. The scope names direction and reach; the picture and the scene tell you whether either one is a problem.

The first thing you read is the lean. A neutral test image collapses toward the middle, but a real scene may lean because of its subjects, lighting, or palette. When a whole-frame pull does not match a credible neutral, a known reference, or the scene's intended color, it becomes evidence of a cast.

A cast has a direction

Two global controls provide a practical first pass for many whole-frame casts:

Temperature is the orange-to-blue axis. Tungsten practicals push the image warm, while open shade and late dusk push it cool. On the vectorscope the whole cloud leans toward orange or toward blue, and you correct that lean with the temperature control.
Tint is the green-to-magenta axis, perpendicular to the first. Fluorescent tubes are the classic offender, dragging the cloud toward green, while some LED sources push the other way, toward magenta.

```sketch { "kind": "compass", "lean": "warm", "spread": 0.42, "targets": true, "caption": "Warm lean toward orange, so the correction runs the other way, back toward blue." } ```

Each cast has a direction, so ask the same first question every time: which way does the cloud lean? Name that direction before touching anything. Temperature and Tint are a practical first pair on a prepared image, but the vectorscope does not prescribe a control. Camera Raw white balance, linear channel gain and per-channel Offset can answer related imbalances at different points in the pipeline. The next balance-method room teaches that choice.

Run that read on the car wash below. Its magenta and cyan neon should reach well out toward their own hue targets, and they do not. The whole cloud sits in tight around the middle. Distance from the middle is saturation, so the first fault is that the chroma has been pulled out of the frame. Push saturation back out and the second fault shows up: the further the cloud reaches, the more plainly it leans off center. That lean sits on the orange-to-blue axis, so temperature is the control that answers it.

```demo { "plate": "car-wash", "scope": "vector", "controls": ["temp", "sat"], "baseLook": { "temp": -22, "sat": -26 }, "challenge": { "kind": "seat", "chip": "CENTERED", "zones": [ { "read": "reach", "band": [28, 40] }, { "read": "lean", "band": [0, 9] } ] }, "caption": "Two target zones are live, marked REACH and LEAN. Push saturation out until the REACH ring lights up, then clear the lean until the LEAN box lights up too. Muted chroma can make a cast harder to see." } ```

The boxes catch what the eye misses

The waveform shows level rather than hue, so a color problem can sit inside an exposure that measures cleanly. On a vectorscope, a whole-frame pull in one direction may suggest a cast. That reading needs something expected to be neutral or a reference that supports it. A naturally colorful scene can lean for perfectly intentional reasons.

A frame full of bright balloons can make a small shared hue shift hard to see. On the scope, each arm is a spike reaching toward a hue, and a common rotation across known colors can expose the shift. The boxes help name hue direction; the expected colors in the image are what make the diagnosis credible.

The boxes are drawn for a specific measurement: standard 75% color bars should sit on the matching targets when the system is aligned. Natural images are not test patterns. Reaching or crossing a box does not prove that a trace is oversaturated or illegal. It does not prove clipping either. Use the scope to measure direction and reach, then judge the picture, channel detail, and delivery limits together.