What Is a Colorimeter, and How Does It Work?

Colorimeters are straightforward color comparison tools that are often confused with spectrophotometers. However, colorimeters have a more limited range of capabilities than spectrophotometers.

What exactly is a colorimeter, and how does it work?

What Is a Colorimeter?

A colorimeter is a light-sensing device that is used to measure the absorbance and transmittance of light as it moves through a sample of liquid.

The main components of a colorimeter include:

  • Illuminant: A specific, fixed light source that passes through the object.
  • Cuvette: A sample holder where the liquid is placed.
  • Standard observer: A two-degree standard observer, which is a small and specific field of view.
  • Photocell: A system that detects light passing through the sample.
  • Tristimulus absorption filter: A filter that isolates specific wavelengths to be applied to the sample.

There are two different types of colorimeters:

  • Color densitometers: Measure the density of primary colors.
  • Color photometers: Measure color transmission and reflection.

Colorimeters may also be compact and portable to use on the go or larger for benchtop use in a lab.

How Does a Colorimeter Work?

A colorimeter’s function is based on Beer-Ambert’s Law, which postulates that the absorption and concentration of a liquid sample are directly proportional. To analyze color against an existing standard, the colorimeter sends an illuminate through a liquid sample.

The colorimeter’s lens and tristimulus absorption filter turn the beam of light into an isolated wavelength. The photocell evaluates how much of the wavelength was absorbed, and the device returns the results on its digital display.

Colorimeters and spectrophotometers are two of the most advanced color measurement devices. Although they are closely related, they each have unique pros and cons that make them best suited to different types of measurements.

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What Are Colorimeters Used For?

Colorimeters are typically used to compare the results of a new sample to an existing one. Common colorimeter applications include monitoring the growth of a yeast or bacterial culture, assessing beverage color and measuring ink colors used in printers and scanners, particularly during the production and inspection stages of manufacturing.

Colorimeters do not provide full-range spectral data, so they are better suited to applications that require fast results with less analytic depth.

Colorimeter vs. Spectrophotometer

There are many critical differences between colorimeters and spectrophotometers. One of the main distinctions is that spectrophotometers are more versatile with multiple illuminant and observer combinations as well as several geometric arrangements. The precision optics of a spectrophotometer collect the light that reflects off of or is transmitted through an object. The spectrophotometer then can calculate the exact number of photons at specific wavelengths and determine the three-dimensional coordinates of the object’s color.

A spectrophotometer measures reflectance and transmittance for the entire electromagnetic spectrum, while colorimeters operate only in the visible portion. Spectrophotometers can also measure qualities that colorimeters can’t, such as metamerism.

Because spectrophotometers offer full-spectrum analysis, they are ideal for a wide range of applications that are tightly toleranced, particularly in research and development stages where they can be used for color system development and color formulation. They are also perfect for providing quality control during production.

Color Solutions From HunterLab

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