Colorimeter vs. Spectrophotometer: What's the Difference?

Modern colour measurement technologies go beyond the subjective human gaze and allow us to objectively quantify a rainbow of colours. Image Source: Unsplash user Denise Chan

Colour surrounds us every moment of our lives and affects our emotions, behaviors, and beliefs in large and small, conscious and unconscious ways. Colour can set a mood, warn us of danger, give us critical information, and even bring us joy. Despite the universal presence of colour, describing it remains elusive, in part due to variations in colour perception from person to person and in part due to a lack of descriptors for each of the millions of shades seen by the human eye.

Instrumental colour measurement moves beyond the limits of human perception and vocabulary and allows us to capture colour information as objective data, creating a common language of colour that is essential for communication within and between industries around the world. The two most advanced colour measurement instrument types are colorimeters and spectrophotometers, both of which use sophisticated technologies to accurately and precisely quantify and define colour.

While closely related, these instruments have unique qualities that may make one more suitable than the other for a particular type of measurement.1 Understanding the characteristics of a colorimeter vs. spectrophotometer can help you select the best tool for your application.

Colorimeters are ideally suited for evaluating final colour results and identifying unwanted colour variations. Image Source: Pexels user Karolina Grabowska

What Is a Colorimeter?

A colorimeter is designed to perform a type of psychophysical sample analysis by mimicking human eye-brain perception, which means its measurements correlate to human perception.. In other words, it is designed to see colour the way we do.

Its results are direct and read as tristimulus values. A tristimulus value is one that identifies a colour with characters that represent different dimensions of its visual appearance. A tristimulus value may contain values like X, Y and Z or L, a and b. The “gold standard” for tristimulus colours is the CIE Colour System, developed by the International Commission on Illumination — the CIE in the title stands for the French version of their name.

There are a few unique components involved in a colorimeter.

• Illuminant: The illuminant represents a specific light source, such as daylight or incandescent light, to project consistent brightness onto the object. In a colorimeter, an illuminant is fixed.
• Observer: The standard observer offers a specific field of view with which to analyze the colours. A colorimeter usually uses a 2-Degree Standard Observer, which is suitable for colour evaluation and quality control.
• Tristimulus absorption filter: The absorption filter isolates specific wavelengths to be applied to the sample.

How Does a Colorimeter Work

A colorimeter’s usage is often based on the Beer-Lambert law, which tells us that the concentration of a solute is proportional to its absorbance. The colorimeter starts with a simple light source. With the help of a lens and tristimulus absorption filters, the beam of light becomes a single, focused wavelength which then moves through to the sample solution. On the other side of the solution is a photocell detector that identifies how much of the wavelength got absorbed. The detector is connected to a processor and digital display that offers a readable output of the results.

Now that you know how it works, let’s take a look at the pros and cons of a colorimeter.

The Pros of Colorimeter

Below are some of the benefits of a colorimeter.

• They focus on tristimulus values. If you don’t need full-range spectral data, a colorimeter doesn’t have you paying for tools you won’t use.
• They tend to be more portable. Colorimeters are less complex, so they may be easier to move around or use in the field.
• They work quickly. Many applications for colorimeters require fast-moving equipment, such as on an assembly line, and a colorimeter can do that.

The Cons of Colorimeters

While the advantages of a colorimeter are clear, there are a few disadvantages associated with them.

• They don’t offer a complete range of data. While colorimeters are great if you don’t need a lot of data, they aren’t going to offer you spectral information about your sample. A colorimeter won’t have adjustable light sources and filters that allow for additional measurements. It won’t be able to find colorant strength or help with colour formulation.
• They aren’t versatile. 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 since they lack accuracy and adjustable components.
• They can’t identify metamerism. Metamerism occurs when colours look identical in one lighting condition, but not another. For instance, fluorescent lighting may make a product look quite different than it would in the sunlight. Colorimeters can’t identify and adjust for this occurrence.

Applications for Colorimeters

Typically, the colorimeter compares results to an existing sample. Colorimeters are extraordinarily accurate for straightforward colour measurement and ideally suited for determination of colour difference, fastness and strength as well as routine comparisons of similar colours. As such, they can be invaluable for colour quality control and are primarily used in the production and inspection phases of manufacturing.

What Is a Spectrophotometer?

A spectrophotometer is an instrument designed for physical sample analysis via full spectrum colour measurement. By providing wavelength-by-wavelength spectral analysis of a sample’s reflectance, absorbance, or transmittance properties, it produces precise data beyond that observable by the human eye. If desired, spectrophotometers can be used to calculate psychophysical colorimetric information as well.
Spectrophotometers are incredibly precise and offer an expansive range of data. They use similar components to a colorimeter but with slight variations.

• Illuminant: The illuminant of a spectrophotometer is versatile. You can use standard and fluorescent illuminants that represent various types of light.
• Observer: The observer of a spectrophotometer is typically larger, at about 10 degrees. CIE recommends it as the most appropriate tool for industrial colour applications.
• Prism, grating or interference filter: To isolate specific wavelengths, a spectrophotometer uses a prism, grating or interference filter, which allows it to change which wavelength gets selected.

How Does a Spectrophotometer Work?

The basic layout of a spectrophotometer is similar to a colorimeter, but with more steps and variations, as well as some different components. An illuminant projects a light source onto an object and through a prism, grating or filter. The tool used will isolate just one wavelength band to hit the sample. A sensor then detects the light that doesn’t get absorbed by the item and passes the data onto a processor or computer equipped with the appropriate software. It can detect things like reflectance, transparency and illuminance along with a tristimulus value.

Next, we’ll go over the pros and cons of a spectrophotometer.

Pros of a Spectrophotometer

Some of the advantages of a spectrophotometer are as follows.

• They are incredibly comprehensive. A spectrophotometer has more advanced hardware and can measure qualities that a colorimeter can’t, including metamerism and reflectance.
• They are versatile. You can typically adjust illuminance and observer settings to get just the right options on a spectrophotometer.
• The work with powerful software. By integrating with software, spectrophotometers offer a new, comprehensive way to review and analyze data outside of a built-in display.
• They come in a variety of styles. Spectrophotometers are available for a wide array of sample types, including powders, liquids and transparent materials. Portable options are also available.

Cons of a Spectrophotometer

Of course, no piece of technology is without a few drawbacks. Here are a few cons of spectrophotometers.

• They are more complex. With complexity comes sensitivity, and they may not be as suited for factory environments.
• They can be more expensive. Though price varies by model, spectrophotometers and their precise, broad range of information typically cost more than a colorimeter.
• They may have more technology than necessary. If you only need simple colour measurements that a colorimeter can provide, a spectrophotometer may be more than you need.

In the past, spectrophotometers have been large and complicated, but modern technology allows them to be smaller and more user-friendly.

Applications of Spectrophotometers

Spectrophotometers offer a higher level of flexibility and versatility than colorimeters due in part to the fact that they offer multiple illuminant/observer combinations and can operate in multiple geometric arrangements, including 45°/0° and d/8°. As such, 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 colour differences missed by colorimeters. Spectrophotometric instruments are ideally suited for a broad range of applications in the research and development phase, including colour formulation and colour system development, as well as colour quality control throughout production.

What Are the Main Differences Between Colorimeters and Spectrophotometers?

There are several similarities between colorimeters and spectrophotometers, but the two are still vastly different. The biggest difference is in capability and usage. Spectrophotometers are incredibly powerful and can offer more in-depth measurements than a colorimeter, such as spectral data. This is why they are primarily used for precise measurements in research and development or laboratory use. Colorimeters, in comparison, are simpler and are common in production and manufacturing, such as for quality control.

Some other differences include:

• Versatility: Spectrophotometers have many adjustable options and can work well for different types of samples and measurements.
• Cost: As mentioned, spectrophotometers are often more expensive than colorimeters due to their powerful technology.
• Accuracy: Colorimeters aren’t as accurate or precise as spectrophotometers.

When considering a colorimeter vs. spectrophotometer, it’s important to consider a variety of factors that may influence its applicability to your situation, such as illuminant source. Image Source: Pexels user Sebastian Müller

Choose the Best Colour Measurement Device for Your Application

Choosing a colour measurement instrument requires an understanding of the advantages and disadvantages of both colorimeters and spectrophotometers as detailed above. If you are still uncertain about which instrument is best for your purposes, these questions, inspired by David R. Wyble of the Rochester Institute of Technology, can help you gain clarity when considering your options.:2

• Type of data required: Does the application require spectral data or tristimulus values only?
• Instrument geometry: Does the instrument have the geometry necessary for your application?
• Precision and accuracy: What level of precision and accuracy are necessary for satisfactory results?
• Light source: Does the instrument have an appropriate light source for your application?
• Rapidity of measurement: How quickly can data be obtained? What kind of sample preparation is required?
• Ease of use: Is the instrument designed with the user in mind, facilitating simple and rapid operation?
• Robustness: Is the instrument appropriate for the environment in which it will be used? Can it withstand harsh factory conditions?
• Software interface: Does the accompanying software allow you to easily collect, analyze and share data?
• Product quality: Not all colour measurement instruments are created equal, regardless of whether they are colorimeters or spectrophotometers. By selecting the best quality instrument, you can be assured that you will obtain the highest quality results.

HunterLab Colour Measurement

At HunterLab, we have been pioneers in the field of colour measurement for over 60 years. We offer a comprehensive range of modern colorimetric and spectrophotometric instruments designed to meet the versatile needs and exacting standards of our customers across industries whether in the field, the lab or on the factory floor.

Our commitment to continuous innovation and technological excellence has led to the development of the highest quality colorimeters, spectrophotometers, and software products available on the market today, expanding the possibilities of colour analysis, formulation and quality control. Contact us to learn more about our colour measurement instruments, customizable software packages and dedicated customer support services and let us help you select the right tools for your applications.