Color Measurement
and Analysis
CT&A GRAPH TOOLS
Use the Graph tools to measure the spectrums of color patches (Reflectance mode), displays (Emission mode), and light sources (Ambient and
Flash modes). Depending on the samples measurement mode, various operations can be performed, either on a single measurement or by
combining two measurements. If your requirement is to formally assess the quality of a display or viewing environment, such as a light booth,
then you should also have a look at the ISO 3664+ tools shown in the next screenshots.
The screenshot above was obtained by measuring Sample-1 (S1) in Flash mode and Sample-2 (S2) in Ambient mode. The sample on the left
(S1), drawn in black in the top graph, is a measurement of a small digital camera accessory flash. The flash Illuminance was measured at 745
lux-sec; its color temperature is 6187 K and its CRI, calculated using D62 as a reference, is 97 (this reference is shown between parentheses
below the CRI). The bottom graph of the same screenshot shows "S1 vs Illum.", where the S1 spectrum is reproduced and compared with the
spectrum of an ideal D62 source of the same brightness, shown in green. We see an excellent match between the spectrums for wavelengths
higher than 430 nm.
The sample on the right (S2), drawn in red, is a measurement of a common tungsten-halogen desk lamp. With a 2860 K Correlated Color
Temperature (CCT), this lamp has a spectrum extremely close to Illuminant A; it has a definite yellow tinge compared to D60, the illuminant
selected as a reference to compute and display the L*a*b* values (in other words, the "xy" coordinates of the lamp, 0,4474 and 0,4075 in the
screenshot, fall in a yellower area of the chromaticity diagram when compared to the coordinates of the D60 Illuminant). Its Color Rendering
Index (CRI) is 100 when computed using a 2850 K blackbody as a reference. By selecting the "S2 vs Illum." button, we can make a comparison
between the S2 ambient measurement and the 2850 K blackbody used as a reference for the CRI; this is shown below.
You will notice that the color of the patches and their L*a*b* values have changed. This is because we have also selected Illuminant A as the
reference to compute and display the L*a*b* values. This time, the chromaticities of the flash measurement are much more towards blue than
the chromaticities of Illuminant A (please also note that the measured chromaticities have not changed between the two screenshots above
since these are absolute measurements.
The image below is an example of what is obtained by clicking on the "Save image" button located in the bottom of the Graph tools dialog.
The image can be saved at two resolutions, 1X, as shown below full size, or at twice the resolution and size (2X) for better printing quality.