Smartphone Camera

The smartphone camera is currently the most common means of reading QR codes. Starting with iOS 11 building QR code recognition into the camera app as standard in 2017, Android also integrated Google Lens, and an environment took shape in which QR codes can be scanned without a dedicated app. Today, with global smartphone penetration exceeding 70%, the smartphone camera is the de facto standard as a means of scanning QR codes.

The reading mechanism detects the finder patterns (the squares in three corners) in the image captured by the camera, identifies the QR code area, and decodes it. Because processing starts when the autofocus achieves focus, scanning fails in environments where the camera cannot focus (dark places, extremely short / long distances). A practical scanning distance is roughly 3-10 times the length of one side of the QR code. A 3 cm QR code can be read at a distance of 9-30 cm.

There are three practical points for improving scanning accuracy. First, secure a quiet zone (margin) of at least 4 modules around the QR code. Second, ensure a sufficient contrast ratio between the code and the background (a black code on a white background is the most reliable). Third, avoid gloss on the printed surface. With glossy paper, reflections from the camera flash or the lighting wash out the code, which causes reading to fail.