What is Inter-Instrument Agreement and Why Does it Matter?

What is Inter-Instrument Agreement?

Inter-instrument agreement (IIA) refers to how closely two or more color measurement instruments of a similar model read the same color. The tighter the IIA of your fleet of instruments, the closer their readings will be to one another. While IIA is less important if you are only operating a single spectrophotometer in a single location, it is essential if you need your instruments to communicate across the supply chain. The closer (or smaller) the IIA is, the more likelihood of your colors being consistent across products, material or locations.

Inter-instrument agreement is the first step in producing consistent color quality, but it is not the only one. Implementing the right conditions and processes is also important, including sample measurement techniques and controlling temperature and humidity of the environment you’re measuring within.

In a world of color precision, if you perform color measurements across multiple locations (different offices locally, nationally or internationally), you need to ensure the highest consistency and accuracy in your color measurement results. Often, there is little room for error.

When a company does not trust its color measurement instruments to provide consistent results, it often leads to:

• Sending physical samples from one location to another for color verification, which takes up weeks of time
• Mistakes discovered too late in the production process to be remedied and as a result, quality suffers
• If mistakes are caught in time and new batches must be produced, this adds unexpected time and budget constraints

This becomes highly problematic for companies.

Why is Inter-Instrument Agreement Important?

If you are a major brand or manufacturer, you are expected to produce color-correct products that drive sales. There are two keys to achieving this:

1. By leveraging the use of highly precise spectrophotometers for color measurement across your supply chain
2. By adhering to numerical tolerances for acceptable color difference for your products. These are known as Delta E tolerances.

To minimize color inconsistency while specifying or producing color, it is critical that the color measurement instruments used throughout your organization—as well as your global supply chain—produce compatible results.

How Does Datacolor Manage Inter-Instrument Agreement Differently than their Competitors?

A key differentiator between Datacolor instruments and competitive instruments is our extremely tight inter-instrument agreement. While it’s true that competitive spectrophotometers also have good IIA, Datacolor manages it a little differently.

Datacolor spectrophotometers are all calibrated to a master instrument of the same geometry. That means all our d/8 spectrophotometers, for example, regardless of the model, correlate back to the same master. This enhances inter-instrument agreement between facilities that are using different spectrophotometer models of the same geometry. (For example, at the brand/lab level, they use a Datacolor 1000 but at the supplier level, they use a Datacolor 700 or Check 3).

While a handheld device like a Check 3 is not as precise as a high end instrument like the Datacolor 1000, but by setting IIA at the geometry level instead of the product level, there is better consensus when using multiple devices that are of the same geometry.

Why does IIA at the geometry level matter? Because our competitors set their IIA at the product level, meaning that their version of a high-end d/8 spectrophotometer may not correlate well with their other instruments of the same geometry, therefore making it harder to find consensus on color between facilities and potentially causing confusion or inaccurate color.

How Does Inter-Instrument Agreement Streamline Global Color Operations?

Spectrophotometers with excellent inter-instrument agreement produce color measurement data that can be shared throughout the global color development process. Here’s how this process might work for a company with multiple locations. Keep in mind that, depending on the color approval process, the industry supply chain, and the number of instruments involved, there are a variety of possible scenarios:

• Color standards are measured with one spectrophotometer in a lab in the United States.
• The reflectance data is then shared with supply chain partners in China and Thailand, for example
• Rather than remeasuring a physical standard, the supply chain partners use this “digital” standard to produce the requested color
• The produced color is measured by the supplier and electronically sent to the customer for approval

When the lab and manufacturers are all using similar models of spectrophotometers with excellent inter-instrument agreement, it reduces the time and costs associated with producing and shipping physical samples. But more importantly, everyone involved can be confident in the digital data being communicated.

Important Things to Know in Relation to Inter-instrument Agreement:

1. What is Delta E?

“Delta E” is the expected degree of color difference from one color measurement to another. The Delta E tolerances you set for your color measurements depend on a range of factors, among them color, material, and the intended application. You’ll find the Delta E tolerance capabilities in the specs of your spectrophotometer. The smaller the Delta E tolerance, the higher the inter-instrument agreement.

2. What is Repeatability in Color Measurement?

Repeatability refers to a single instrument’s ability to give the same reading, regardless of the number of times a sample is measured. It’s important to have a repeatable measurement technique that is replicated throughout your supply chain. You can learn more about measurement techniques and factors impacting repeatability here.

3. What is a Close-Tolerance Spectrophotometer?

The designation as a “close-tolerance” spectrophotometer is reserved for those precision instruments that are manufactured to the highest quality standards and that have the best inter-instrument agreement. The “close-tolerance” label applies only to those instruments that have very low maximum allowable variance compared to a master instrument, based on international standards.

Only a select few instrument models available in the world today produce these exceptional results without the need for adjustments based on instrument profiling. The Datacolor Spectro 1000 family of spectrophotometerssatisfies the requirements of a true close-tolerance instrument with excellent performance and inter-instrument agreement out of the box.

When these close-tolerance instruments are in use throughout an organization, colorimetric data can be confidently shared between them. This also ensures that fleets of instruments can be merged or replaced without concerns of significant changes in historical results or ongoing colorimetric decisions. To avoid significant variation in measurement results, it is important to take these requirements into consideration when adding spectrophotometers or replacing old ones.

With proper operation and maintenance, your spectrophotometer will provide consistent inter-instrument agreement for many, many years. Of course, there will come a time when an upgrade is necessary to continue producing the most accurate color measurements possible.

Here are some additional reasons you may want to upgrade an older machine:

• Increased ease of use
• Improved measurement speed
• Renewal of an expired support contract
• Ethernet connectivity