Chromaticity Graph
Access the Chromaticity Graph View from the Measurement View
using the Chromaticity
Button.
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.
The first selection is between the two Chromaticity color
spaces, CIE 1931 x y space, and CIELUV u'v' space.
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.
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.
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.
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.
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:
Selecting one of these chooses the standard colorspace.
Use the Android Back button to return to the Measurement View.