White Paper

Color Measurements byAgilent UV-Vis and UV-Vis-NIR
Spectrophotometers
Using the Agilent Cary WinUV Color application to
fully characterize color based on calculations ofspectral dataIntroduction
Light can be reflected, scattered, transmitted, or absorbed from matter, or cause
photochemical reactions. Ultraviolet visible (UV-Vis) spectrophotometers use a lightsource to illuminate a sample with light across the UV to visible wavelength range,
typically 190 to 1,100 nm. The instruments then measure the light that is absorbed,
transmitted, or reflected by the sample at each wavelength.
Humans perceive color when light interacts with objects by the use ofphotoreceptors in the eye, primarily through the processes of transmission orreflection. Color measurements using UV-Vis spectrophotometers use the same
principle as the human eye. However, UV-Vis spectrophotometers can objectively
obtain a value that describes the color by offsetting the color of light used toilluminate the sample.

This white paper describes the options for color
measurements that are available from Agilent, including anoverview of the Cary WinUV Color application that translates
spectral data according to various geometrical coordinates
and illumination systems. The best choice of instrument
for a particular application will depend on sample type andanalysis requirements.

Color testing using UV-Vis
Color measurements are an important part of quality control
processes in many industries, ensuring color consistency ofproducts for branding, aesthetic, or clarity purposes. UV-Vis
can also be used in industrial processes to measure a changeof color in a solution. It is often used to assess if a reaction
has occurred or is proceeding without the need for visualinspection by an operator. As a fast, non-destructive analyticaltechnique, UV-Vis has also been used in art restoration andconservation projects to help match paint colors.1 Example
applications of UV-Vis color testing can be found in sectors
such as foods and beverages, pharmaceuticals, textiles,automotive, plastics, paints, electronics, personal careproducts, cosmetics, plus many more.

Agilent Cary UV-Vis andUV-Vis-NIR spectrophotometers
Agilent offers a range of instruments for color measurementsthat cover liquid and solid sample types. The Agilent Cary 60
UV-Vis and Cary 5000 UV-Vis-NIR spectrophotometers areshown in Figure 1 and a full list of instruments is provided
in Table 1. These Cary instruments, which are controlled
by Agilent Cary WinUV software for UV-Vis or UV-Vis-NIR,
address a variety of analytical needs, e.g., high throughput,ease of use, and sample accessibility.

Figure 1. Agilent UV-Vis spectrophotometers used for color measurements
include the Agilent Cary 60 UV-Vis spectrophotometer (top) and Agilent Cary
5000 UV-Vis-NIR spectrophotometer with an external diffuse reflectanceaccessory (DRA) (bottom).

Table 1. Agilent UV-Vis and UV-Vis-NIR spectrophotometers that are widely used for color measurements.
SystemCary 60

Cary 4000
Cary 5000
Cary 6000i
Cary 7000 UMS

2Sample Types

Accessory Options

Analysis Requirements

Liquids and solids– Cuvette– Fiber optic probe and coupler for liquids– Remote fiber optic diffuse reflectance accessoryfor solids1– High-throughput with the 18-cell changer
or fiber optic dip probe– Ease of use– Sample accessibility– Remote measurements– Food and beverages– Water analysis– Pharmaceuticals– Petrochemicals– Fine/specialty chemicals

Application Examples

Liquids and solids– Cuvette– Solid sample holder– Integrating sphere/diffuse reflectance accessory– Fiber-optic probe and coupler– Universal Measurement Accessory (0/45°)– Color research– Small or very large samples– Extended wavelength into NIR– Measurement flexibility– Textiles and fabrics– Plastics and paints– Haze/gloss measurements

Dedicated software forcolor measurements
Cary WinUV Color application is an optional software
package that expands the Cary WinUV software and allows
users to perform color calculations on data collected byCary spectrophotometers. Users can select from multiple
calculation options within the Color application, as describedin Table 2, including the first standardized color systemcoordinates that were defined by Commission Internationale
pour l'Eclairage (CIE) in 1931. Once selected, any calculations
are performed automatically.
Table 2. Options within the Agilent Cary WinUV Color application.
SystemParameters CalculatedColor Coordinates

Tristimulus

X, Y, Z

Chromaticity

x, y, zCIE

L*a*b* L*, a*, b*

CIE

L*u*v* L*, u*, v*

HunterLab L, a, bMetric

L*, C*, hWhiteness Index

WI

Yellowness ASTM E313-00

YIE313-00

Tint Index

TE313-00

Gardner ASTM D6166

GTM

Haze Calculations

According to ASTM Method D1003(requires an integrating sphere)

Color Difference MeasurementsCIE∆E*ab, ∆L*, ∆a*, ∆b*, hab, C*ab, ∆H*ab

FMC-2∆EFMC-2, ∆LFMC-2, ∆C1, ∆C3

CMC (l:c)∆E(CMC)BFD (l:c)∆E(BFD)

Hunter Lab∆EH, ∆LH, ∆aH, ∆bH

Illuminants– CIE A, B, C, D65, D55, D50, and D75– F1 to F12Observer Angles– CIE 2° (1931)– CIE 10° (1964)– Photopic observer– Scotopic observer– Two user defined observers

Calculation Intervals

1, 5, or 10 nmGraphics– 1931 x,y and 1976 u',v' chromaticity diagrams forboth 2° (1931) and 10° (1964) observers– CIE L*a*b* color space– Hunter Lab color space– %Transmission or %Reflectance versus wavelength

Other features of the Cary WinUV Color application include:– Selection of up to 50 samples at one time for calculations.
– Calculations are performed over one of three selectablewavelength ranges (360 to 830, 380 to 780, or
400 to 700 nm) at one of three data intervals(1, 5, or 10 nm).
– Thickness correction is also provided when comparing thecolor of samples of varying thicknesses.
– The Match feature highlights the difference between theL*a*b* of a sample and a standard.
An analysis of the color of a sample can be achieved bysimply setting up data collection parameters and baseline
correction in the Cary WinUV Color application. The user thenselects the illuminant (or illuminants) and observers, followedby the color coordinates needed for the calculations. Oncethe data have been collected, the color calculations will beperformed automatically by the software, and graphs will
be generated. A final report can then be produced based onuser requirements.
Data collected from the Agilent Cary 3500 UV-Vis
spectrophotometer series (Multicell, Compact, and Flexiblemodules) using the Cary UV Workstation software can also
be imported into the Cary WinUV Color application and color
analysis can be performed accordingly.

Application example
Figure 2 shows an application example for the color
measurement of a green food dye using a Cary 60
spectrophotometer with illuminant CIE C. A section ofthe transmission spectrum and color data obtained using
different coordinate systems (tristimulus, chromaticity, andCIELAB) are shown.

Other Options

3

A

B

CDEIlluminant = CIE C
Tristimulus

X = 32.7609

Y = 55.2320

Z = 12.9154

Chromaticity

x = 0.3247

y = 0.5473

z = 0.1280

CIELABL* = 79.1747

a* = –63.1544

b* = 68.4185

Figure 2. (A) Green food dye color measured using the Agilent Cary 60 spectrophotometer with illuminant CIE C; (B) %Transmission spectrum of dye;(C) chromaticity data; (D) CIELAB data; (E) summary of the tristimulus, chromaticity, and CIELAB calculations for the food dye.

Conclusion

Further information

The combination of an Agilent Cary UV-Vis
spectrophotometer with Cary WinUV Color application
provides an ideal tool for color testing of samples. The
software quickly compares and verifies spectral information
obtained by the instrument and generates color measurement
data using a wide selection of color coordinate systems.

– Agilent Cary 60 UV-Vis Spectrophotometer

Agilent color measurement workflows can be used with liquidand solid samples in many industries such as electronics,materials, food and beverages, as well as art restoration andconservation projects.

– UV-Vis Spectroscopy and Spectrophotometer FAQs

Reference
1. Teragni, P.; Scardina, P. Measuring the Color of a Paint on
Canvas via the Agilent Cary 60 UV-Vis Spectrophotometerwith the Remote Fiber Optic Diffuse ReflectanceAccessory. Agilent Technologies application note,
5991-3783EN, 2021.

www.agilent.com
DE88596329
This information is subject to change without notice.
© Agilent Technologies, Inc. 2023
Printed in the USA, October 24, 20235994-6792EN– Agilent High-Performance UV-Vis,
Cary 5000 UV-Vis-NIR spectrophotometer– Cary WinUV Software for UV-Vis Applications– Agilent Cary WinUV Software for UV-Vis-NIR Applications– UV-Vis Spectrophotometer Uses and Applications