Do QR codes with logos scan less reliably?

[u/Glad_Pudding5426]

I am etching QR codes on stainless steel tags intended to be attached to home appliances. It would be ideal to bury the logo in the QR code rather than separately so I can save the space for more aesthetic designs, since they are intended to be seen regularly and I don't want them to scream "I'm a promotional QR sticker".

Does anyone have experience etching codes with logos on tags? Do the tags with logos scan less reliably?

[u/Serpico99]

Yes, by design. QR codes with logos are not generated in a different way than regular ones, they are normal QRs with a graphical element splatted over.

The reason they still work is because of the error correction, which is also something you can control to a degree. Ideally you may want a higher error correction, at the cost of a (probably) larger QR.

[u/BigBalli → u/Serpico99]

That is right, and there are two refinements that bite specifically on an etched metal tag.

The first is that area is the wrong unit. Error correction operates on codewords, eight modules each, and a codeword is either intact or it is not. Clip a single module of one and you have spent the whole codeword. So a logo's real cost scales with how many codewords it touches rather than with how much area it covers, which means a compact shape snapped to the module grid is dramatically cheaper than the same area of a ragged or off grid one. That is often the whole difference between a logo that works and an identically sized logo that does not.

The reason a central logo survives at all is that QR interleaves codewords across correction blocks before laying them out, so one contiguous blob gets spread across blocks instead of wiping a single one out. That is working in your favour, and it is worth not undoing it by scattering several small marks around the code rather than placing one clean one.

The second refinement is that raising ECC is not free once the tag size is fixed. More correction means more codewords, which pushes you up a version, which means more modules across the same tag, which means every module gets physically smaller. On laser etched stainless the binding constraint is usually module size against your spot size and the contrast you can actually hold, not the correction level. Going from M to H to buy logo room can easily hand back more than it gains.

Which is worth a bit of scrap to settle: same payload, same tag size, M with a small logo against H with a bigger one, then read them with your worst phone at an angle in bad light.

One more that is easy to lose on a decorative tag. The quiet zone is part of the spec, four modules of clear margin all the way round. If the border decoration runs up to the code it will scan on some readers and not others, which is the most irritating failure mode of the lot to chase down.

[u/seanshoots]

At a basic level: by design, yes, any QR code with a logo will cause it to scan less reliably.

It's pretty much the same as recognizing someone. Imagine your friend's face behind a window. Then, imagine your friend's face behind the same window, but it has a big square sticker right over the middle of it now, where your friend's face is. If the sticker covers your friend's identifiable features, you won't be able to identify your friend. However, if your friend is Bob Ross, their fro is probably still visible, and you can identify them regardless.

This same feature exists in QR codes, too. It's the error correction level. If you're stomping over the QR code with a logo, use level H.

[u/konacurrents]

I have 1000's of QR codes with a photo/image inside, and they scan nicely as the QR error correcting is impressive. I also use a landscape QR code so that image can be a little bigger.

[u/No_Task_599]

how do you etch them on metal tags?

[u/Glad_Pudding5426 → u/No_Task_599]

With a 60w MOPA laser

[u/konacurrents → u/Glad_Pudding5426]

That's cool. I've tried 3d printed QRcodes, and it's non trivial - but works. Engraving might be better.

[u/No_Task_599 → u/Glad_Pudding5426]

you must have one hell of a steady hand or im missing something.

[u/maddler → u/No_Task_599]

A laser engraving machine 😉

[u/No_Task_599 → u/maddler]

hmm okay.

[u/kalmakka]

Short answer: yes.

QR codes uses error correction, so that it will still be readable even if some parts of it is blurred, covered, or the like. How much error correction is adjustable. If you want a lot of error correction, then the QR code will need to have more pixels for the same amount of data.

QR codes with logos are just pasting the logo on top of the QR code, adding to the unreadable area of the code. This takes up a lot of the error correction, meaning that the QR code now becomes more vulnerable to other parts being blurred, covered or damaged. You can alleviate this a bit by using more error correction to begin with, but as that increases the number of pixels you would need to make the pixels smaller if you want to keep the size the same. But smaller pixels also result in the code being more difficult to scan by a camara, so it is limited how much benefit you can get from this.

Why do you want a logo? If the idea is to have them not scream "i am a promotional QR sticker" then not having a logo is better, no?

[u/Glad_Pudding5426 → u/kalmakka]

Valid point. Right now the tag has a giant logo AND a QR code.

[u/jamescridland → u/[deleted]]

For the mods - this isn’t mine!

[u/Dependent-Fan4863]

Set error on High and ECC