Why a 2 cm QR still fails: contrast and viewing distance
Small codes need strong contrast and enough printed size for the distance people will stand.
12 November 2026
Answer: Check contrast and planned print size together. If people scan from farther away, enlarge the code — do not only darken the modules.
Tool: QR print checker — free, runs in this browser.
Low contrast (grey on grey, or logo colors close in luminance) defeats cameras before size becomes the issue. High contrast with a tiny footprint fails when the viewer cannot fill the frame.
A two-centimetre code on a window across a lobby is a different job from a two-centimetre code on a handout. Distance drives minimum module size.
Print the multi-size test sheet, tape it where the final piece will hang, and scan with the same phones your audience uses. Keep the size that worked; discard the ones that did not.