A guest cannot scan the code

The margin, first every time

A camera locates a code by its edges, and it needs clear space to spot them. A code trimmed flush to a border, or set flush against a photograph, gives it nothing to focus on. The band needs to be about 4 of the code s own small squares across on every side.

Our sign templates ship with this band already. A design hand-built is where it disappears.

1. Look at the margin. The code needs a clear band around it, about 4 of its own squares across.
2. Measure the width. About 5 cm for arm s length. About a tenth of the scanning distance beyond that.
3. Offer the link instead. Announce the address or send it in the group chat. It opens the same page.

Too small for the distance

A code that scans on your desk might fail on a wall. The width must grow with the distance — about a tenth of it — so a sign folks read from 2 meters away wants about 20 cm, not the 5 cm that suits a table card.

A guest with a phone in a dim room also holds it less steady, which costs a little more size again.

Rounding up costs paper. Rounding down costs the contribution, since no one attempts a second time.

Contrast, not color

A camera reads light versus dark. A mid-tone code on a mid-tone background can seem elegant on a screen and be illegible on card, and a code laid over a cluttered photograph is the same problem with extra noise. Keep whatever rests behind the code plain and far from it in tone.

A light code on a dark field works, only if it was exported like that instead of inverted afterward.

The light in the room

Gloss card under a spotlight throws the light direct back, and the phone spots a white patch where the pattern belongs. Candlelight brings the opposite problem: too little light at the wrong angle. Matt card and ordinary room lighting fix both.

If a sign fails only in the evening, that's why. Nothing about the file has changed.

When it is the phone

Some older cameras need the code centered and kept steady for a moment, and some third-party camera apps don't read codes at all. Request the guest to use the built-in camera app and to keep the phone 20 to 30 cm away instead of pressing it against the card.

A cracked or greasy lens is worth mentioning too. It sounds trivial and it's an actual cause.

The fallback that always works

Give them the address. Each sign should bear the web address in plain text below the code, and you can post the same link in the group chat in 5 seconds. It reaches the same page, and it works on a phone whose camera is refusing.

That's also the answer for anybody reading a digital invitation, since a phone can't scan a code on its own screen.

Preventing all of it

Print 1 sign, prop it where it will stand, and scan it using a borrowed phone at a standard sitting distance, in the light the room will have. That one check catches margin, size, contrast and gloss in 1 go, before printing 40 of them.

Repeat it the day before if anything about the artwork changed in between.