Prepress Barcode Verification

 In 201

Often we are asked when the best time to verify barcodes is, and our answer is always “as early and as often as possible.” Recently someone took our advice literally and asked us to verify a UPC symbol on a Cyrel® flexo plate. We have been asked about prepress barcode verification before, and our stock response has been that verifying anything other than a live, printed barcode is meaningless because so little can be learned from the plate. You can determine that the symbology and check digit are correct, and that bar width reduction has been imposed at a certain level—that’s about it. So many more things can go wrong: quiet zones, press gain, symbol contrast, defects, modulation to name a few.


Always in the past, our stock answer quickly ended the conversation. Not this time. This time the client countered with, “but if we wait until production, much more money will be at risk.” We were stunned, not only be the rejoinder but also by our prior blindness to the truth it exposed. Of course the client was correct about the economic issue. Yes a significant amount of money was already spent on at the plate stage, but from there the investment was only going to multiply, and quickly as the bag or package or header or whatever it was rolled out of the press in potentially huge numbers, and with devastating financial implications if the barcode didn’t perform well, for more reasons than just those reasons cited above.

The economic risk factor is a result, an outcome of poor quality, whatever the cause: a human error, a machine failure, a process problem. Consider the additional vulnerabilities in a prepress process with multiple vendors.  Each of them is an unexamined error opportunity, from graphics design to plate making before ink starts flowing. Is the barcode font based? Can the plate making software correctly render the design file data? Was the barcode scaled to make it fit? Did that step effectively destroy the integrity of the barcode? Prepress barcode verification makes a lot of sense.

What’s the big deal? Why can’t you just use a verifier on the flexo plate? You can’t because there is virtually no contrast difference between the bars and spaces. They are all that same orange color. And proofing often doesn’t even use the plate—it uses the same data sent to a special proofing printer. Doesn’t that effectively close the gap between prepress and on press? It helps, but no, it doesn’t close the gap entirely, and there are gremlins in that gap. The same graphics design software may have driven both the plate-making machine and the proofing printer, but the processes involved in plate making are very different than proofing. The vendors promise an exact match, but people who work in the real world of prepress and on press know that they are not always in lock step.

Until something better comes along, the only current solution is to ink the printing plate bearing the barcode, pull a proof and verify that.

If you know of something more elegant than that, or you just want to comment, please share! We want to hear from you.

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Showing 2 comments
  • David Wicker

    Great article!
    It appears that the science is advancing in this area due to 3D imaging, here is a recent article on : 3D Texture Recognition Using Bidirectional Feature Histograms that should lead to being able to not only capture the “print area” of the flexo plate but also the quality of the barcode image “shoulder”.


    • John Nachtrieb

      Thank you, David. I will read it with great interest.

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