Holographic overlay partially covering barcode

Had a card where the holographic overlay extended further down the card back than it should, partially covering the lower portion of the PDF417 barcode. Documenting this because it's an unusual failure mode and the resolution was informative.

What the problem looked like

The barcode on the card back was mostly clear, but the bottom few rows of the PDF417 were obscured by the holographic overlay that had been applied slightly too low. On first scan with my phone, the barcode failed to decode. I assumed it was an encoding issue until I looked more carefully and saw the overlay edge cutting across the bottom of the barcode zone.

Why it matters

PDF417 barcodes have error correction built in, which means they can still decode even if a portion is damaged or obscured — up to a point. The amount of data that can be recovered depends on the error correction level the vendor used when encoding the barcode. A low error correction level means even partial obscurement causes failure. A higher level can handle more loss.

In my case, the overlay was covering roughly 15% of the barcode rows. A higher error correction level would likely have allowed the barcode to still decode. It failed, which suggests the vendor used a low error correction setting.

Testing other scanners

I tried three scanner apps. All failed. This confirmed the issue was the overlay coverage rather than app-specific sensitivity — if even the most tolerant scanner can't decode it, the data loss is beyond what error correction can recover.

The resolution

Sent photos to vendor support. They acknowledged the overlay application error and the insufficient error correction level (a double quality miss) and replaced the card. The replacement had the overlay correctly positioned and the barcode scanned on first attempt with all three apps.

The lesson: overlay application quality is a production control issue, not just a cosmetic concern.