Decodability—A Deeper Dive
The ISO 15416 linear barcode parameter Decodability differs from other parameters because it measures element (bar and space) widths and positions. All of the other ISO parameters are based on reflectivity. Why measure bar and space widths and positions when scanners do not work that way? Because it is a helpful diagnostic tool when linear barcodes scan poorly or not at all.
Why Measure Width, Not Reflectivity?
Measurements are helpful. The bigger question is, why do they go wrong—and what to do about it in barcode printing? First, let’s understand the measurements.
It is not so much a problem when bars and spaces uniformly measure wider or narrower than nominal. Decodability is not about uniformity. Consistently wider or narrower bars are usually a result of print gain: bars grow and spaces shrink, causing differences in reflectivity, and resulting in Modulation downgrading. Decodability is different.
Non-uniform Width Deviations
Non-uniform deviations in bar and space widths affect decodability. Often, bars and spaces are also slightly relocated relative to each other. As we have discussed in previous articles, this is caused by discrepancies between the barcode design file and the printer—specifically an incompatibility in resolution. A 203DPI printer has pixels that are .00493” wide. Divide one (inch) by 203 (pixels) and you get the size of each pixel. A bar (or space) must be a multiple of pixels: 2 pixels = a bar or space width of .00986”, 3 = .0148”, etc.
Causes
If the barcode design file was created at a different DPI than the printer, it will send commands to the printer that it cannot execute. Bars and spaces will be relocated positionally and adjusted widthwise.
That is the simplest explanation, but there are other causes:
- Scaling: resizing the barcode to fit a larger or smaller label. The best practice is to create the barcode at its final size.
- Font-based barcode software: vector-based design software is always best.
- Saving: file compression such as PDF can degrade the dimensional integrity of the design file.
Confirm acceptable, compatible file formats supported by your printer. Document procedures and instruct all users to follow and not deviate from them.
This can be challenging with label design applications embedded in larger CRM, ERP or other business management systems. You may need to query tech support or your system vendor.
Barcode question or problem? We can help.
John helps companies resolve current barcode problems and avoid future barcode problems to stabilize and secure their supply chain and strengthen their trading partner relationships.
