[chbot] My Vaccine Pass QR code - too small to read?

[Helmut Walle]

It's not really as tight as it may seem - you just need to get closer with the scanner or camera
than you would for these larger shop posters. It's really not different in principle from
scanning smaller vs. larger linear bar codes.
Regarding pixel sizes, even back in the 90s, laser printers were already 300dpi - so that's a
little bit better than 0.1mm. From looking at this QR code (quickly) it appears to be something
like 3-4 pixels per mm. So each QR code pixel is about three pixels wide, which gives you at
least nine pixels of area covered, on a completely outdated printer. Printers delivering 600dpi
or better are the norm these days, so that you would be looking at about 30-40 printer pixels of
area covered by each of the code squares.

You might want to check your scaling, though - mine printed at an inch squared at 100%, and they
are scanning just fine on both a generic QR scanning app and the NZ Pass Verifier app from MOH,
and that is in this dim evening light without any artificial lighting.

Kind regards,

Helmut.


On 27/11/2021 18:13, Robin Gilks wrote:
> Has anyone else downloaded their pass? Got mine but after printing the QR code is only about
> 23mm square and it's a much higher density than say the scan posters that shops have. As far as
> I can see it would need to be at least 200mm square for the code to be read, as the size of the
> elements of the code are of the same order as the pixel density of my laser printer.
> 
> Even 500% mag on a pdf reader and my phone (iPhoneX) can't decode it.
> 
> Looks like a fail to me!
> 
> -- 
> Robin Gilks
> 
> 
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