Chromaticity Graph

Access the Chromaticity Graph View from the Measurement View using the Chromaticity Button.

Chromaticity Graph

The Chromaticity Graph View shows a representation of color that is independent of its luminance.
Two standard Chromaticity spaces are supported in ColorMeter, the CIE 1931 x y space, and the more perceptually uniform CIELUV u'v' space.

The graph plots x or u' values on the X axis, and the y or v' values on the Y axis.

Always plotted as well is the spectral locus with values in nanometers (nm), and color coded with an illustrative wavelength color. The spectral locus is closed with the standard purple-red line.

You can pinch zoom and the X and Y scales will track together, retaining the aspect ratio.and touch scroll to focus on any detail of the graph.
Double tap to return to full view.

The axis and wavelength numerical values will fade in or out of view during zooming, maintaining a smooth transition with changes in scale,
and providing the ability to precisely measure the location of features of the graph.

The last measured color is marked by a triangle, with the Measurement reference marked with an upside-down triangle.

Re-measure by touching the Measure menu item.
Return to the measurement View by tapping the system Back button.

The Options menu item pulls down a list of selection boxes that allow choosing optional features to be displayed.

Chromaticity color spaces
The first selection is between the two Chromaticity color spaces, CIE 1931 x y space, and CIELUV u'v' space.

standard illuminant chromaticity locuses
The second selection is whether to display one of two standard illuminant chromaticity locuses, either the more usual Black Body (or Plankian) locus, or the subtly different Daylight locus.

color temperature units
The third selection chooses the color temperature units to annotate the illuminant locus with, either the conventional degrees Kelvin, or the more perceptual micro reciprocal degree or Mired units, which are equal to 1000000/ºK.

Color Temperature Delta Measure
The fourth selection chooses whether to show the correlated color temperature, and if so what distance measure should be used to locate the closest point on the illuminant locus. Correlated uses the standard CIE 1960 UCS color space delta E, which when used with the Black Body illuminant locus results in the standard CCT (Correlated Color Temperature). The alternative Visual uses the modern CIEDE2000 delta E forumula, and will give perceptually closer value. The color temperature is indicated on the graph as a dotted line connecting the color sample with the illuminant locus.

Show primaries
The fifth selection chooses whether to plot any set primary references marked by squares, and if there are three or more, to connect them with a gamut boundary estimate.

Standard Gamut
The sixth selection switches to the Standard Gamut selection. This allows the display of a standard colorspace primaries, secondaries, white point and gamut, marked with circles, plus the gamut triangle.

The Options menu is dismissed whenever a selection is made, or dismiss it without making a selection by touching somewhere else on the view.

The Standard Gamut selection brings up a sub-menu:

Chromaticity Graph Standard Gamuts

Selecting one of these chooses the standard colorspace.

Use the Android Back button to return to the Measurement View.

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