Vectorscope

The Vectorscope plots the chroma of every sample on a polar graticule. HML Balance is the same plot split three ways by luma.

What Is Plotted, and What the Marks Mean

The plot uses the color space the incoming frame declares, and Rec.709 where it declares nothing.

The left menu on Space / Xform offers BT.601, BT.709 and BT.2020, and sets the space for the target boxes, the hue ring, the rim ticks and the hue axes.

The right-hand menu on the same row offers YUV and HSL, starts at YUV, and lays out the chroma plane. Under HSL the hue runs through the graticule’s own anchors, and only the full-saturation targets appear.

Targets and Rings

Six targets are labelled R, Y, G, C, B and M, in that order round the wheel.

The 75% set always appears, at code 766 of 1023, and the 100% set only while the 100% box is on.

The rings are at a quarter, a half and three-quarters of the plot radius, and at the rim, the scope’s own edge.

Circular is the default shape, and Hexagonal a six-sided path at the same radii.

The Three Graticules

The Graticule row offers three views, and a stock scope uses Color Wheel.

Standard — the rings and rim ticks, plus the optional marks you have switched on.
Hue Vectors — three full-diameter axes through the centre, one per opposite pair of targets, each end lettered R, Yl, G, Cv, B or Mg.
Color Wheel — the chroma plane’s own colors as a band round the rim, built from the same six targets.

The Skin-Tone Line

The skin-tone axis is on at stock at 123.0 degrees counter-clockwise from the +Cb axis, running from the centre out. The Skin tone box switches it.

Two drags set its angle over 0 to 360 degrees, and, while the Band box is on, a tolerance of 1 to 45 degrees either side. The band is off at stock, with a 10.0-degree half-width.

The I/Q Lines

I/Q is off at stock, and it adds two full lines through the centre at 33 and 123 degrees counter-clockwise from +Cb, in the grid color.

The Split

HML Balance is the split as a kind, with three balls on the tile and the split always on.

A lone Vectorscope splits by hand with its Split L/M/H box.

Two drags set the boundaries on one row labelled Split L·M·H, between 0.05 and 0.95 of luma, at 0.33 and 0.66 at stock. A sample below the low split is a low, above the high split a high, and the rest are mids.

LOWS and HIGHS appear above their circles, and the midtones circle has no label.

The Clamp box on a lone Vectorscope adds the Luma range row, a minimum and a maximum between 0.0 and 1.0. Vector compares each sample’s own luma against that window, the whole range at stock.

Trace Options

Trace offers Dots, one point per sample, and Traces, which joins each sample to the one before it within a single scan line.

Linearise weights each sample by the inverse EOTF of its luma, showing how much light is present, and moves no plotted position.
Centre boost brightens the trace near the middle of the plot.
Outline inks the edge of the cloud.
Outer scale adds a circle outside the rim.

Zoom, Rings and Reset

The pane’s Zoom · rings row has a Reset zoom button and two drags of 0.0 to 1.5 for the saturation-alert and saturation-maximum rings. Both start at 0, showing no ring.

The dial’s Scope Zoom Reset runs down to 0.25, while the pane and the wheel start at 0.5, and the next notch raises a lower value to 0.5.

What to Read

A bar chart or a test pattern against the 75% boxes, with 100% on for a full-range source.
Skin tone as a direction, not a number, and only while the rest of the frame looks right.
The split view when one grade has to serve faces, midtones and highlights together.