QR codes: data, the quiet zone and error correction

Useful to know

QR code collects data in a two-dimensional grid of light and dark modules. Unlike the usual linear barcode, the information is located in two directions. DENSO WAVE, the developer of the technology, describes support for various types of data, including digits, letters and binary data. Therefore, the code is not by definition an internet connection. A site address is simply one of the contents that can be recorded and then interpreted by the reading application. [1]

Characteristic large square markers help to recognize position and orientation. The grid size is not fixed for all codes: more information may require a larger character. With the same physical print size, this makes the individual modules smaller. Therefore, visually similar images can place different demands on the print and camera. A short address and a long text should not be judged solely by the fact that they both fit in a square. [1]

Around the standard QR character, a free edging called quiet zone. is required DENSO WAVE defines a width of four modules on each side. This space is not a place for an additional decorative frame, but a part of the reading conditions. If the graphic designer places a code directly next to text or cuts off its empty end, it can create difficulty even if the black squares themselves appear intact. The print size must also include this edging. [2]

QR technology uses error correction, by which certain missing or damaged data can be recovered. There are four levels with varying degrees of reservation. A stronger correction requires additional information and affects the capacity or size. The indicated percentages refer to code words, not to any part of the visible area. Therefore, it is not correct to promise that closing any corner or adding a large logo will always be compensated. [3]

Take, for example, a menu printed on a small nameplate. The first question is what data the symbol should actually contain. Sufficient module size, free edge and real footprint check follow. An image that is read on a large monitor does not prove that the small printout will behave the same way. The sample makes sense in the size and conditions in which the visitor will use the nameplate, not just in the designer's file. [2, 3]

Finally, we must distinguish a successful reliance on content. Error correction helps to recover the saved data, but does not evaluate the honesty of a specified site. If the code contains an address, the person still needs to judge the address and the action the page wants from them. The quality QR code solves the task of conveniently transmitting information; it is not a certificate of safety, authenticity of a trader or authenticity of the advertisement printed next to it.