When a QR code is published it should be of a size that’s
appropriate for the scanning environment for where it will be displayed. The
finished printed size of the QR code will be dependent on:
- The distance between the QR code and the scanning device – which determines the size of the QR code in the viewport of the phone camera
- The size of the dots in the code – the more data you put into the code the smaller the dots become
Expected Scan Distance
To effectively scan the QR code it should appear to be at least 0.5 inch 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.
If
you have a QR code on a banner 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 program then the scanning device will be held quite
close to it so it can be much smaller.
Scaling Factor
The scaling factor accounts for lighting conditions and unexpected issues with scanning. A six would give your users the greatest margin of error for low level lighting or shaky scans. Whereas 10 would expect for perfect lighting with no shadows, etc.
SIMPLE Rule of thumb formula:
| Minimum QR Code Size = |
|
Expected Scan Distance from the QR code to mobile phone |
| |
Scaling Factor
|
HOWEVER.....
As mentioned above, the more data you put into the code the smaller
the dots (the dark pixel squares) become as the QR code adjusts itself
to increase its data storage capacity. For example, if your QR code will link to a long URL, you should shorten it by using a URL shortener like bit.ly or goo.gl. Not only will it make your QR have larger dots and make it more easy to scan, it also gives you an easy way to track the number of scans and clicks.
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. QR codes with a high data density are going to have more rows and columns of dots in it, so each dot will
be smaller relative to the size of the QR code itself. If the dots are
too small then the QR code will be difficult to scan because the data
dots are below the resolution limit of the scanning device.
See the examples below:
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http://bit.ly/r9jIYM
|
|
http://www.growthvine.com/BLOG/ViewBlogs/
|
|
http://www.growthvine.com/GROWTHVINE/growthvine/Go.aspx?c=BlogViewer&BlogKey=5e2b017c-e9da-43ab-86e5-7784cf5023d3
|
Data Density Factor and versions of QR codes
Each QR code has a certain number of rows and columns depending upon the amount of data inside of it. The number of rows and columns will always be equal, but vary between version 1 with 21 columns by 21 rows to version 40 with 177 rows and columns. More on the data capacity of each version of QR codes
here.
In order to determine your QR code's
Data Density Factor, count the number of columns of
dots in the QR code image and then divide that by 25 to normalize it.
MORE ACCURATE FORMULA:
| Minimum QR Code Size = |
|
Expected Scan Distance |
|
* Data Density Factor |
| |
Scaling Factor
|
|
Examples:
A QR code containing vCard contact details has resulted in QR code with 57 rows and columns of data dots. It’s to be
printed on a business card in black and white and it’s expected that the
scanning distance will be about 6 inches and used in optimal lighting conditions for a scaling factor of 10.
Scanning Distance = 6 inches
Scaling Factor = 10
Data Density Factor = 57/25 = 2.28
Minimum QR Code Size = (6 / 10) * 2.28 = 1.37 inches
A QR code is to be placed on a conference poster linking to an abstract for a session. The QR code has 25 rows and columns of dots. The lighting is a bit dim and the
scan distance will be about 2 feet.
Scanning Distance = 24 inches
Scaling Factor = 10 – 1 (for poor lighting) = 9
Data Density Factor = 25/25 = 1.0
Minimum Size = (24 / 9) * 1 = 2.67 inches
A QR code is printed on a banner hanging from the ceiling of a conference expo hall linking to the mobile website featuring exhibitors and the expo floor map. This has resulted in a QR code that has 41
rows and columns of data dots. The distance may be as large as 35 feet.
Scanning Distance = 35 feet or 420 inches
Scaling Factor = 10 – 2 (for distance and possible shaky scanning) = 8
Data Density Factor = 41/25 = 1.64
Minimum Size = (420 / 8) * 1.64 = 7.18 feet
In cases like this, you may need to increase the Scaling Factor to 10 to decrease the size of the printed QR code.
#qrcode #datadensity #qrcodesize