A: Experiment Tutorials
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The fields on this screen are described in the following table.
Field Description
Mode Either Emissive or Reflective mode is selected, depending on the
type of color measurement selected in Step 1. You can change it
here:
Reflective – Color measurement of a surface
for a selectable CIE-defined illuminant. For color
by transmission, choose Reflective color. The
math for reflective and transmissive color is
the same. In both cases, it is measuring the
percentage of light that is collected after the
light interacts with something.
Emissive - Measurement of the light emitted from
an LED or a lamp (emission source).
Observer Specify the observer (viewing angle) using the drop-down list:
2° (CIE 1931) – photopic (daylight)
10° (CIE 1964) – scotopic (dark-adjusted)
Illuminant
If you chose Reflective measurement under
Mode, select the
desired Illuminant from the drop-down list. This illuminant is
theoretical and CIE-defined; it has nothing to do with the actual
lamp used in the measurement. The choice of illuminant only
matters for some color spaces (especially X, Y, Z and dominant
wavelength and purity).
In Emissive mode, the X,Y,Z color space is normalized based on
the illuminant (X,Y,Z are multiplied by 100/Yref where Yref is the Y
value for the illuminant). The E illuminant effectively removes the
reference illuminant from the calculation, so if you want to see the
unnormalized X,Y,Z values then choose illuminant E.
Also, the dominant wavelength depends on the "white point",
which is the chromaticity of the illuminant. A change in the
illuminant can shift the dominant wavelength about 5nm. The E
illuminant places the white point in the center of the x,y
chromaticity diagram (at 0.33,0.33,0.33).
It is normal to report the illuminant and observer with the
measured color, and it is not strictly necessary that the illuminant
be the same type of lamp as the test lamp (that is, illuminant A is
not just used with tungsten lamps). The two most common
illuminants are A and D65. You may want to see how others in
your field report their results in terms of the illuminant used.
For future use.
