When selecting the correct size for a QR Code, its not only the physical size that needs to be selected.
With the physical size I mean the actual size in squire inch (or centimeter) room that is reserved for printing the QR Code.
QR Codes are available in various versions (grid sizes), and 4 error correction levels. You would assume that the highest error correction setting would be best choice to guarantee a working code. But is it?
There is a big chance that by selecting the highest error correction level, also a bigger version, and therefor a bigger grid size needs to be selected for the content to fit the code.
Since the total grid size will be scaled down to fit the physical dimensions as mentioned before, the resolution of the total code will degrade, thereby increasing the risk of hard to read or unreadable QR Code.
The surface where the code will be printed on will also an effect on readability. A code placed on a folder will be easier to scan than a code printed on a plastic bag.
The quality of a Custom QR Code can be degraded by three basic factors:
Error correction since part of the code is usually replaced by a graphic.
- Errors introduced by placing the graphic in the code need to be corrected. The bigger the graphic the more errors are introduced, this need to be compensated with a higher error correction setting.
- Usually the highest error correction is selected, to maximize the size of the graphic to be placed. In order no to exhaust the error correction a bigger version of the QR Code is needed.
Black against white still gives the highest contrast.
When a graphic is being made part of the code's content, as can be done by the service I offer, this has a positive influence on the error correction. A QR code with the highest error correction setting, but containing error due to graphic placement will be more sensitive for misreads then a QR Code with a lower error correction setting but without errors.