User Manual

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In a way, the Chromaticity scope is a 3D scope, but it’s drawn as if you’re looking down at the
top of a 3D shape that plots every color value in an image in X, Y, Z space, but you can only
perceive the 2D outline around the widest parts of this shape drawn on an X, Y plot. The graph
does indeed represent every single value found within a 3D plot of the image data, but the
triangle only indicates the widest “slice” of the current gamut and of this 3D shape within the
mid-tones.
What this means is that while the Chromaticity scope’s graph gives you a rough idea of whether
or not the current image is within gamut relative to your delivery spec, it’s not exact and it’s not
foolproof, as part of the image data could fall within this wide triangle and yet overshoot the
required gamut elsewhere in the highlights at the top or the shadows near the bottom of the 3D
shape you’re looking down on. On the other hand, if any part of the graph does extend past the
boundaries of the gamut triangle, then that definitely indicates a gamut violation. You can add
an additional gamut triangle in the scope settings in order to compare the color space you’re
working in to another color space, for reference.
Most people who’ve had any exposure to color grading concepts are familiar with the traditional
CIE 1931 horseshoe graph, which plots the portion of the spectrum visible to the human eye
according to studies done in the late 1920s (subsequent studies have confirmed this analysis).
The optional CIE 1976 uv graph is based on an updated color space (CIELUV) that was an
attempt by the International Commission on Illumination (CIE) to create a more perceptually
uniform graph of color. Whereas the CIE 1931 analysis visually exaggerates certain parts of a
color graph, the CIE 1976 graph draws all parts of a color graph more or less proportionally to
one another. Overall, neither analysis is more “correct” than the other, it’s simply a matter of
what you prefer to look
The CIE 1976 scope showing both P3 and Rec.709 gamuts
Panning and Zooming the Video Scope Graphs
If you want to examine any part of a video scope’s graph in more detail,
you can do the following:
To zoom into a graph: Hold the Option key down, and roll the scroll control.
To pan around a graph: Click and drag with the middle pointer button.
Chapter – 114 Viewers, Monitoring, and Video Scopes 2604