Public Lab Research note

Video Tutorial: Mobile Phone as Colorimeter

by fongvania | May 20, 2022 03:05 20 May 03:05 | #30829 | #30829

The video below shows an easy way to use your phone as a colorimeter, which can help you measure the concentration of substances in colored samples. To learn more about colorimeters, scroll past the video~

Materials needed:

  • Transparent liquid container(s). The video uses cuvettes, which can be glass or quartz. Avoid using plastic since acetone can damage or melt plastic.
  • Holder for container
  • Sample solvent. This video uses nail polish, which contains acetone, a chemical good for chlorophyll extraction.
  • White background
  • Mobile phone with app that detects RGB values

More Detail on Colorimeters and Spectrophotometers

Colorimeters convert visible light into values that correspond with human perception of color, which typically means Red, Green, Blue (RGB) or Lightness, Red/Green Value, Blue/Yellow Value (Lab), and they are most useful in developing relative measurements of color intensity. Colorimeters are best used to compare similar colors and shades and to measure color strength. A really good use for colorimeters is to determine the relative concentration in solutions because there is a law (Beer's Law) that says that the more concentrated a solution is, the more light it will absorb. The video uses colorimetry to measure the concentration of chlorophyll from leaves.

Typically, colorimeters provide a light source that is only of one wavelength, however, in this modified mobile phone version, ambient lighting is used, so you want to make sure this ambient lighting is as similar as possible across measurements of different samples. Avoid measuring samples at dramatically different times of the day or with different combinations of natural and artificial light.

So how is a colorimeter different from a spectrophotometer?

Colorimeters are simpler than spectrophotometers. Both colorimeters and spectrophotometers measure spectral information in visible wavelengths (which means your sample must have a color you can see), but while colorimeters only give you 3 values indicating the intensity of the 3 color components that make up the entire spectral profile, spectrophotometers will give you intensities of light at specific wavelengths. To do this, it uses a prism-like device that splits up the light into its "rainbow" components and measures the intensity of a wavelength or a narrow band of wavelengths. This post describes how light is translated into an electrical signal in more detail. You can also use the spectrophotometer to measure every wavelength to give you a spectral graph. With intensity, you can then calculate transmittance and absorbance of your sample.


Its very easy to get these two instruments confused. If you are measuring color in industry(as in paint color, siding color, etc), its often with a colorimeter(Hunter is a popular brand) and the scales will be Lab. They are to measure color the way the eye sees it, although some of the models may also have an option for spectrum.

If the interest is in analysis, then the term is usually a spectrometer or spectrophotometer. Thats when the term ROYGBIV(Red,Orange,Yellow,Green,Blue, Indigo, and Violet) starts to get bantered. And the units are usually transmittance or absorbance.

There is some difference in optics. The eye normally sees reflected light. So most (not all) of the eye based optics ( and Lab scale) is based on reflected light.

Similarly, most water or liquid measurements are based on transmitted light.

Having said that, many of the newer instruments are based on fluorescence and luminescence. Whole different set of rules apply.

Reply to this comment...

Little change here. Most water or liquid measurements are on transmitted or absorbed light.

Reply to this comment...

If using an instrument like a hunter colorimeter, be careful. There is the Hunter L,a,b scale. Then there is the cie L,a,b* scale. Most instruments will calibrate to either scale, so its just making sure you have the right one. And there are many different illuminants (to simulate the different kinds of light the products might be exposed to). One illuminant is for daylight, another for flourescent lights, etc. And usually , there are some special scales. The YI scale(yellowness index) was one commonly used in plastics. It was used to show how much a clear plastic plastic had degraded.

Good to know about CIE vs Hunter, I didn't even realize there were two different systems.

Since this case is simple enough and relies on the comparison across samples rather than the exact colorimeter values, as long as the app is using the same color scale across reads and as long as the lighting condition is fairly similar, the comparison will be valid. But, still good to recognize the variables and scales that impact the results.

Reply to this comment...

Login to comment.