Barcode Colors – What Works and What Doesn’t?

 In 301

How can you determine what barcode colors are acceptable for linear barcodes? Do you have to actually print a barcode before you can tell if it will work?

No! You can fairly easily test possible colors for the barcode and/or the background to see if they will work. Bear in mind, however, you might or might not exactly duplicate the color swatches you are using are for your test.

 Testing Barcode Colors is Quick and Easy

There are a lot of factors involved in producing an exact barcode color match so be aware, this test will only get you in the ballpark. A good rule of thumb is, if your test results indicate that the colors you are testing produce a marginally safe result, it’s probably wise to use color or color combination that produces less marginal results.

 Symbol Contrast is how barcode colors are measured and graded

The bottom line issue is color contrast, or in barcoding, Symbol Contrast. How is it measured and where is the threshold between acceptable and unacceptable results?

Symbol Contrast or SC is a straight subtraction of the minimum reflectance value (Rmin) from the light reflectance value (Rmax). These values should be expressed as percentages. The Rmin is always the color for the bars; the Rmax is always the background color. The threshold is 40% to achieve an ANSI/ISO C grade, but if you’re printing a barcode on corrugated, the threshold is 20% for an ANSI/ISO D.

Let’s say you want to print an ITF14 on corrugated using a combination of green and red for the barcode and background. If you use a reflectance densitometer, make sure it has a 660nm (+ 10nm) red light source. A white light reflectance densitometer will not work for this.

 Barcode colors must be measured using 660nm red light

Some verifiers can be used as reflectance densitometers and can collect Rmin and Rmax values automatically—and some will even do the SC calculation for you.

Looking at the Details panel in the upper right quadrant of the Axicon Verifier report, our green and red barcode colors will produce a Symbol Contrast value of 70%–perfectly acceptable for printing a barcode.

Notice in the Scan Reflectance Profile panel at the bottom of the Axicon Verifier report, that the Static Reflectance option is enabled (checked). This sets the verifier to operate as a reflectance densitometer without testing an actual barcode.


Axicon Static Reflectance Profile

Simple and quick! But remember—this is the result for these particular barcode colors. For you to achieve these same results you must duplicate these exact colors as best you can. But having achieved an SC of 70%, you‘ve got a lot of latitude! This is a pretty safe color combination.

Best of luck—and as always, your comments or questions are most welcome. And please write in to suggest other topics you’d like to see addressed here.

All the best!

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