Is it possible for a machine to flawlessly match a paint color? Let's explore how technology can make this process perfect.

You may have mixed your own custom paint color from leftover cans in the basement, only to realize it's impossible to recreate. Or perhaps you've moved into a home with a color scheme you adore, but it needs some touch-ups. Now, you're probably wondering how to match paint color without ending up with a noticeable difference.

You head to your local paint shop with a handful of paint chips, convinced you'll find the perfect match, but none of them work. Who could have guessed there were so many variations of green? Thankfully, with the help of a spectrophotometer, you can achieve an exact match — and we're here to show you how it works!

Delving Into Color Beyond the Paint Chip

As we discovered with our box of Crayolas, purple isn’t merely purple, and red isn’t simply red. You have choices like cornflower blue, midnight blue, blue-gray, blue-green, and more. Colors are essentially light waves, and each wave has a unique value that sets it apart. A color can be defined by its purity or desaturation, as well as its value or lightness.

Describing something as green or blue-green is insufficient when you need the exact shade. There could be numerous variations of blue-green alone. So, if you can’t depend on paint samples, how do you expect to find the precise color you’re looking for?

Don’t worry, because the perfect match exists. The tool that can find it is a spectrophotometer. Used for years in the auto industry to flawlessly touch up car paint jobs, spectrophotometers are now readily available in most paint stores. The best part is that the service is usually free. Continue reading to learn how a spectrophotometer works.

The Functionality of a Spectrophotometer

To fully grasp how a spectrophotometer functions, it's important first to understand how color works. This is a vast topic, so we'll cover just a brief summary. Color is made up of light wavelengths and can be divided into six categories:

As shown, visible light falls in the middle, and it’s this spectrum that the spectrophotometer analyzes to match paint. The visible light spectrum consists of the familiar ROY G. BIV — red, orange, yellow, green, blue, indigo, and violet. These seven colors encompass everything we can perceive with the naked eye. Black represents the absence of color, while white contains all of these colors. This will be relevant shortly.

Parts of a Spectrophotometer

A spectrophotometer is actually a fairly straightforward device, roughly the size of a shoebox. Its basic components are as follows:

Since it contains all the colors in the visible spectrum, white light serves as the illumination source in a spectrophotometer, usually provided by a tungsten bulb or, in more advanced models, a Light Emitting Diode (LED). A clip on the outside of the machine holds the paint sample, while white light is directed onto it. The light reflects off the sample, enters the machine, and shines onto a small rotating wheel. This wheel is a highly efficient color analyzer with interference filters, powered by a stepper motor known for its accuracy.

Visible light is measured in nanometers, an incredibly small unit in the metric system, equal to one-billionth of a meter. Each filter is calibrated to allow only specific wavelengths of light to pass, and each wavelength falls within a specific nanometer range. The visible light spectrum spans from red at 400 nm to blue in the 700 nm range, with the most advanced wheels having filters that manage 10 nm intervals.

Color Matching for Paint

In the past, spectrophotometers used transmission filters, where the wavelength matching the color sample would pass through the filter, while all other wavelengths were absorbed. For instance, if you shine white light on a red apple, the apple absorbs every other color and only reflects red back to you.

Today, spectrophotometers for paint matching use interference filters, allowing only the color from the sample to reach the filter, while all other wavelengths are deflected. This improves the accuracy of the match, as absorption could distort the readings.

The correct wavelength for the color match passes through the appropriate filter and is then captured by fiber optics and directed to a photodiode. The photodiode transforms the data into an electronic signal, which is sent to software that calculates the precise pigment quantities needed to achieve the match. And that’s how it’s done, folks.

How Easy It Is to Find an Exact Match

Even though the technology might appear complex, using a spectrophotometer is actually quite simple. It's connected to a touch screen monitor that guides the user through the process, making it very intuitive. You choose your paint base, and for the best results, it's wise to avoid the cheaper options. Mid-grade and premium paints give the most accurate matches.

These devices are quite effective at matching colors from various sources, although they perform best when dealing with samples that don't have significant texture or shine. For example, glossy magazine clippings can cause reflections, and a detailed wallpaper design or thick carpet can make it harder to get an accurate reading. Photos are also not ideal because they don’t capture the exact color.

Precision in Paint Color Matching

Older spectrophotometer models were limited to samples that could fit into a small clip attached to the device, but modern models have evolved. They no longer require direct contact with the sample, meaning you can bring in larger objects, such as a lamp or a door. These newer models use LED lights to emit a focused, powerful beam that efficiently reaches the sample while blocking out surrounding ambient light, ensuring an accurate reading.

Color matching is generally around 90 percent accurate, with the level of precision largely depending on the spectrophotometer model and its corresponding computer software [source: House Beautiful]. Spectrophotometers typically feature between 16 and 31 filters, with the most precise models having 31 filters. The more precisely wavelengths are divided for measurement, the more accurate the match will be.

The accuracy of the process is also heavily influenced by the computer software. For example, if there were 100 interference filters available, but the software could only process 15 of them, the high-performance machine would fail to provide accurate results.

The Price of This Color-Matching Device

For larger items, like a full wall, that need to be matched but are too big to bring to a paint store, you can opt for a handheld spectrophotometer. These devices range from $300 to $1,000. While these smaller models are less advanced than countertop units, they typically find the closest match to existing paint colors instead of producing an exact formula.

Certain brands of paint offer handheld units designed specifically to match their own line of colors, while others offer access to a wide range of 13,000 colors from leading paint manufacturers. Some units even assist in selecting complementary colors that coordinate with your chosen shade, simplifying the decorating process.