What is the difference between a spectrophotometer and a colorimeter?
A colorimeter reads color through 3 to 4 fixed filters and outputs tristimulus values directly. A spectrophotometer measures the full visible spectrum, usually 400 to 700 nm, and calculates color values from that wavelength data. Storing the full spectral curve lets a spectrophotometer detect metamerism, when two samples match under D65 daylight but not under A incandescent. A colorimeter cannot.
Those two words get used loosely. Precisely, the instruments being compared are a filter-based tristimulus colorimeter and a colorimetric spectrophotometer. "Colorimeter" on its own is the umbrella for any instrument that reports color from the human observer function, so it technically covers both, but in practice people use it for the filter-based type. All HunterLab instruments are colorimetric spectrophotometer.
How instrumental color measurement works
Instrumental color measurement minimizes the subjectivity and variability of human perception and vocabulary and allows us to capture color information as objective data, creating a common language of color that is essential for communication within and between industries around the world, ranging from food and beverage to pharmaceuticals.
A filter-based tristimulus colorimeter uses 3 to 4 filters to simulate how the human eye sees color, outputting tristimulus values without obtaining spectral data. A colorimetric spectrophotometer measures the full visible-light spectrum (typically 400 to 700 nm) and calculates color values (L*, a*, b*, XYZ, or any CIE scale) from wavelength-by-wavelength spectral analysis.
Why metamerism detection matters
A colorimetric spectrophotometer can identify when two samples match under one light source (such as D65 daylight) but not another (such as A incandescent), because it stores the full spectral data across many illuminant and observer combinations. A filter-based tristimulus colorimeter cannot make this distinction. It is restricted to its fixed illuminant and observer condition and has no spectral data to draw on.
A filter-based tristimulus colorimeter can handle simple pass/fail QC. A colorimetric spectrophotometer gives you the same colorimetric data plus the spectral data to diagnose why a batch failed, detect metamerism, and support in-depth color analysis, all from one instrument. For any application where color accuracy matters, a colorimetric spectrophotometer is the more future-proof investment.
Not every spectrophotometer measures color
"Spectrophotometer" on its own is a broad category, and not every instrument in it is built for certified color work. All colorimeters can measure color, but most spectrophotometers cannot. Colorimeters meet the specific geometric conditions that color measurement requires. Most spectrophotometers are designed for analytical use. They can measure absorption color, but they are rarely suitable for measuring CIE color. If you are buying a spectrophotometer, you have to confirm it can actually be used for certified color measurement.
The instruments designed for it are called colorimetric spectrophotometers, or spectrocolorimeters. Both instrument types can deliver highly repeatable color measurements. What separates them is that the spectrophotometer keeps the full spectral data and can run the analyses that data makes possible.
While closely related, these instruments have unique qualities that may make one more suitable than the other for a particular type of measurement. Understanding the characteristics of a filter-based tristimulus colorimeter vs. colorimetric spectrophotometer can help you select the best tool for your application.
What Is a Filter-based Tristimulus Colorimeter?
The International Commission on Illumination (CIE) defines a colorimeter as "an instrument for measuring colorimetric quantities, such as the tristimulus values of a colour stimulus." ASTM further distinguishes a tristimulus (filter) colorimeter from a spectrophotometer, or spectrocolorimeter, on the basis that spectrophotometers measure spectral data from which colorimetric values are calculated.
A filter-based tristimulus colorimeter is an instrument for psychophysical analysis that provides measurements correlating with human eye-brain perception by directly reading and providing colorimetric data as tristimulus values (such as XYZ and Lab).
There are a few unique components involved in a filter-based tristimulus colorimeter.
- Illuminant: The illuminant represents a specific light source, such as daylight or incandescent light, to project consistent brightness onto the object. In a filter-based tristimulus colorimeter, an illuminant is fixed.
- Observer: The standard observer offers a specific field of view with which to analyze the colors. A filter-based tristimulus colorimeter usually uses a 2-Degree Standard Observer, which is suitable for color evaluation and quality control.
- Tristimulus absorption filter: Three broad-band optical filters designed to approximate the CIE Standard Observer color matching functions.
Unlike inexpensive consumer RGB sensors, industrial colorimeters are tristimulus instruments, not simple RGB devices. Their optical filters are carefully engineered to approximate human color perception as defined by the CIE, and the instrument reports X, Y and Z rather than R, G and B.
How Does a Filter-based Tristimulus Colorimeter Work?
A filter-based tristimulus colorimeter is a rugged, less complex instrument designed to approximate human visual response. A stable light source illuminates the sample. Reflected or transmitted light passes through three broad-band optical filters, each matched to one of the CIE Standard Observer response curves. Three detectors read the filtered light, the instrument calculates the X, Y and Z tristimulus values, and color spaces such as CIELAB follow from those. The original spectral information is not retained. Only the calculated colorimetric values are kept, and the instrument works under a fixed illuminant and observer combination (typically C/2°).
The Pros of Filter-based Tristimulus Colorimeters
- They focus on tristimulus values. If you don't need full-range spectral data, a filter-based tristimulus colorimeter doesn't have you paying for tools you won't use.
- They work quickly. Many applications for filter-based tristimulus colorimeters require fast-moving equipment, such as on an assembly line, and a filter-based tristimulus colorimeter can do that.
- Simple operation.
- Lower acquisition and maintenance cost for many routine applications.
- Ideal for production environments requiring rapid pass/fail decisions.
The Cons of Filter-based Tristimulus Colorimeters
- They don't offer a complete range of spectral data. A filter-based tristimulus colorimeter won't help with determining colorant strength or color formulation.
- They aren't versatile. Filter-based tristimulus colorimeters lack versatility, as their primary purpose is to compare products to a predefined sample. They aren't well-suited for research or product development applications.
- They can't identify metamerism. Metamerism occurs when colors look identical in one lighting condition, but not another. Filter-based tristimulus colorimeters can't identify and adjust for this occurrence.
Applications for Filter-based Tristimulus Colorimeters
Typically, the filter-based tristimulus colorimeter compares results to an existing standard. Filter-based tristimulus colorimeters are capable for straightforward color measurement and ideally suited for determination of color difference, as well as routine comparisons of similar colors.
As such, filter-based tristimulus colorimeters can be used for color quality control and are primarily used in the production and inspection phases of manufacturing.
What Is a Colorimetric Spectrophotometer?
A colorimetric spectrophotometer is an instrument designed for physical sample analysis via full-spectrum color measurement. By providing wavelength-by-wavelength spectral analysis of a sample's reflectance or transmittance properties, it produces precise spectral data beyond that observable by the human eye. Using this detailed data, colorimetric spectrophotometers then calculate psychophysical colorimetric information.
The result is a complete spectral fingerprint of the sample. Because the whole spectrum is measured and stored, new color calculations can usually be run later without measuring the sample again.
Many spectrophotometers also extend beyond the visible spectrum into the ultraviolet (UV) and near infrared (NIR) for specialized analytical applications.
Colorimetric spectrophotometers are incredibly precise and offer an expansive range of data. They use similar components to a filter-based tristimulus colorimeter but with slight variations.
- Illuminant: Any illuminant can be simulated including daylight and fluorescent illuminants that represent various types of light.
- Observer: The observer of a colorimetric spectrophotometer offers 2° and 10°. CIE recommends 10° as the most appropriate setting for industrial color applications as it better mimics the human observer function.
- Monochromator: A diffraction grating, prism or interference filter separates the returning light into narrow bands of individual wavelengths.
How Does a Colorimetric Spectrophotometer Work?
A colorimetric spectrophotometer is an objective physical analysis instrument to measure color. A stable light source illuminates the sample. The reflected or transmitted light enters a monochromator, typically a diffraction grating, which separates it into individual wavelengths. A detector array measures light intensity at many narrow wavelength intervals, producing a complete spectral reflectance or transmittance curve. From that curve the instrument calculates the X, Y and Z tristimulus values, which convert to CIE Lab, LCh, Yxy and other scales.
Pros of a Colorimetric Spectrophotometer
- They are incredibly comprehensive. A colorimetric spectrophotometer has more advanced hardware and can measure qualities that a filter-based tristimulus colorimeter can't, including spectral data.
- They are versatile. You can typically adjust illuminant and observer settings to get just the right options on a colorimetric spectrophotometer.
- They work with powerful software. By integrating with software, colorimetric spectrophotometers offer a comprehensive way to review and analyze data.
- They come in a variety of styles. Available for a wide array of sample types, including powders, liquids and transparent materials.
- They offer quick results. Some colorimetric spectrophotometers yield results in as little as two seconds, boosting speed and efficiency.
- They aid in achieving the desired color. Obtaining the desired color continuously is vital for brand consistency and process control.
- They are ideal for precise analysis. For research-focused environments where accuracy is paramount, colorimetric spectrophotometers offer in-depth analysis.
- They can also detect metamerism, determine colorant strength, and help with color formulation
- Colorimetric spectrophotometers, depending on its specific model and optical geometry, can perform appearance analysis to provide metrics such as opacity, haze, or NTU
Cons of a Colorimetric Spectrophotometer
- They can be more expensive. Colorimetric spectrophotometers and their broad range of information typically cost more than a filter-based tristimulus colorimeter, though the added capability often justifies the investment for production and R&D environments.
- Earlier colorimetric spectrophotometer designs were built for controlled lab conditions. Modern instruments are increasingly compact, user-friendly, and designed for production environments.
- They may exceed simple QC needs. If your only requirement is pass/fail against a single fixed standard with no metamerism risk, a colorimetric spectrophotometer provides more capability than the task requires. For any application likely to grow in complexity, the additional capability is an asset.
Applications of Colorimetric Spectrophotometers
Colorimetric spectrophotometers offer a higher level of flexibility and versatility than filter-based tristimulus colorimeters due in part to the fact that they offer multiple illuminant/observer combinations and spectral data. Furthermore, they are available in various models equipped with different optical geometries—such as diffuse (d/8° or d/0°) or directional (0°/45° or 45°/0°)—to suit specific material characteristics. As such, colorimetric spectrophotometers are capable of measuring metamerism, identifying colorant strength, analyzing a comprehensive range of sample types and giving users a choice between including or excluding specular reflectance to account for geometric attributes.
Full-spectrum analysis also provides for greater specificity, potentially identifying color differences missed by filter-based tristimulus colorimeters. Colorimetric spectrophotometers are ideally suited for a broad range of applications in the research and development phase, including color formulation and color system development, as well as color quality control throughout production.
Why Spectral Data Matters in Color Measurement
A colorimetric spectrophotometer measures and stores the complete spectral fingerprint, far more information than the three tristimulus values a filter-based tristimulus colorimeter measures. Because the complete spectrum is available, a single measurement can be used to calculate a wide range of color spaces, color indices, and advanced analytical metrics.
Color spaces
- CIE L*, a*, b*
- CIE L*, C*, h°
- XYZ
- Delta E
Color indices
- Yellowness Index (YI)
- Whiteness Index (WI)
- APHA
- Gardner
- Tint
- Color Strength
- Opacity
- Haze
Advanced analysis
- Metamerism evaluation
- Spectral comparison
- Color formulation
- Traceability and spectral archiving
Think of the measured spectrum as the sample optical fingerprint. Every reported color value, including CIELAB, Delta E, Yellowness Index, Whiteness Index, APHA and Gardner, is calculated from this spectral fingerprint.
Because the complete spectrum is preserved, the data can be reanalyzed in the future without remeasuring the sample, providing maximum flexibility, traceability, and confidence in your color measurements.
Which color measurement solution does your industry need?
All HunterLab color measurement devices are colorimetric spectrophotometers. The right choice comes down to your sample type, your tolerance requirements, and whether you need spectral data for reformulation or in-line process control.
| Industry / application | HunterLab instrument | Key features |
|---|---|---|
| Food and beverage, pet food: powders, liquids, dairy, sauces | ColorFlex® L2 | Touchscreen; built-in camera for sample preview; measures opaque solids, liquids, powders, granules, and pellets, plus translucent solids and liquids; live camera preview; onboard EasyMatch Essentials L2 with no separate PC |
| Beverages, oils, transparent liquids, plastic preforms | Vista® L2 | Measures color and haze/NTU simultaneously in a single transmission read; onboard EasyMatch Essentials L2 with no separate PC |
| Plastics or recycled plastics, packaging films, coatings, paints, textiles, paper, petrochemicals, pharmaceuticals, dark and low-reflectance materials | Agera® L2 | Certified Grade 'A' CIE D65 illumination with controlled UV; color and 60° gloss in one read; live camera preview; onboard EasyMatch Essentials L2 software with no separate PC; Dark Performance Mode resolves dark and low-reflectance samples |
| Food and beverage: snacks, nuts, non-homogenous textures | Aeros® | Non-contact instrument; automatic height positioning; minimal sample preparation required; result in about five seconds; 35 measurements per rotation |
| In-line process control: bread, nuts, snack food | SpectraTrend® HT | Continuous non-contact monitoring; flags off-color batches instantly; closes the gap between the line and the QC lab |
| Solids and liquids: reflectance and transmission | UltraScan® VIS | Measures reflectance, transmittance, and haze/NTU; wavelength range 360 nm to 780 nm; 10 nm optical resolution and reporting interval; two reflectance measurement areas; automated UV calibration and control; |
| High-precision research and QC: transparent and opaque | UltraScan® PRO | Measures reflectance, transmittance, and haze/NTU; automated specular include or exclude; spectral range 350 nm to 1050 nm, full CIE visible range plus NIR; automated UV calibration and control; 5 nm reporting interval |
| Meats, poultry, fish, produce: portable or multi-line | MiniScan® EZ | Handheld; available in directional 45°/0° and diffuse d/8° geometries; measures product the way customers see it |
Not sure which instrument fits your process? Talk to a HunterLab color measurement specialist.
