QR Codes

Exerpt from The Death of the BRC, Target Marketing, October 2012.

The more data you put into the [QR] code, the smaller the dots (the dark pixel squares) become, as the QR Code adjusts itself to increase its data storage capacity. And, as the size of the dots decrease, they become harder for the scanner in the smartphone to "see," so the QR Code itself needs to be made larger in order for it to be reliably scanned. Here are seven other factoids and tips to help you decipher QR Codes:

1. The density of the code is described by a version number that is based on the number of rows and columns of dots. A Version 1 QR Code will have 21 rows and 21 columns of dots and the version number will then increase by 1 for every 4 extra rows and columns. So, for example, a Version 2 QR Code will have 25 rows and columns, a Version 3 QR Code will have 29 rows and columns, right through to a Version 25 QR Code that will have 117 rows and columns.

2. Most QR Codes containing just a website address end up being Version 2 QR Codes, with 25 rows and columns of data dots. However, QR Codes containing long URLs (like URLS for Google Maps addresses) may result in a larger Code, such as a Version 6 or Version 7 QR Code with 41 or 45 rows and columns of dots.

3. QR Codes containing vCard (electronic business card) contact details have really high data densities and will result in Version 10 or Version 11 QR Codes with more than 60 rows and columns of dots.

4. Unfortunately, the resolution of average present-day camera-enabled portable devices is such that the size of the data modules (dots) on a QR Code of Version 5 (37x37) or above presents a real risk of incorrect decoding by the device. So, when creating a QR Code intended for use with mobile phones, you should stick with Version 4 or lower, and a QR Code symbol of at least 2 cm (0.85˝) across.

5. To effectively scan the QR Code, it should appear to be at least 1 cm (0.4˝) across in the viewport of the scanning device, and as the distance between the camera and the QR Code increases, the size of the QR Code will need to increase to compensate. For example, if you have a QR Code on the side of a building, it would need to be very large because it's going to be scanned from a long distance. However, if it's printed in a magazine, then the scanning device will be held quite close to it, so it can be much smaller.

6. For most smartphones, the relationship between scan distance and minimum QR Code size is approximately 10:1, so a 2.5 cm (1˝) QR Code printed in a magazine will have a nominal effective scan distance of about 25 cm (10˝), and a QR Code on a billboard 65 feet from the where a passerby would be scanning it would probably need to be about 6.5 feet across.

7. Use a URL shortener such as TinyURL to reduce the number of characters in a long URL. Doing so will result in a code with larger dots, hence it can be reproduced at a smaller size without impacting scan reliability.