If you have experienced the system not recognising the QR Cards you uploaded, you know that it can be time consuming to manually tag each one. The reason is most likely because the QR Cards were not photographed in the most optimal way for detection. Below, we will describe the best practices for shooting QR Cards.
(Already photographed the QR Cards and wondering how to manually tag them? Please refer to the following article: Why are the QR Cards not automatically detected by the system?)
So, how can we achieve the best recognition rate?
We ran tests using the following different variations:
- Different ISO
- Different shooting angles
- Different angle of the light source
- Size of the QR code on the photo
- Wrong focus (blur) & motion blur
- No white border around QR code
- Holding card vs. placing on table
- Different shadows on the QR code
- Folding paper
- Bending paper
- JPG Compression & Image Quality
The following resulted in successful recognition:
We had a 100% success rate with evenly exposed, sharp QR codes of a decent size!
Effect of Exposure:
Underexposure / Overexposure and ISO did not have an effect on the recognition as long as the white of the paper was “in the light parts” of the histogram and the dark dots were significantly darker.
Angle of QR Card:
As long as the paper is flat, the angle did not have a negative effect.
Size of the QR code:
The recognition is done on a 1200px scaled photo. The dots still need to be recognisable with that image size. The code could even be so small that its edge length is 15% of the photo (2% of the image area).
Our recommendation is to shoot a close-up of the QR Card so you can still read names, access codes, and/or handwritten notes on each one.
Holding the card:
It is important that the QR code is flat (not bent).
- putting the QR Card on a flat surface if the paper is thin, or
- using stronger paper if holding them by hand.
If they are held by hand, make sure you do not have light areas in the background which are lighter than the paper of the QR Card.
The following resulted in failed recognition:
Uneven exposure / Shadows within the QR code
Bent & folded paper within the QR code
Reflection of light in the black QR dots
No white border around the code
The QR code needs to have a white border around it. If your individual card design does not leave enough space around the QR code, it can affect the recognition in a negative way.
This is a common problem if the studio in the background is well lit, but the QR code is way darker (in front of the lights). Since there is not enough contrast on the QR code, the image is not optimised and recognition suffers.
Wrong Focus / Motion Blur
Small QR code in combination with high jpg compression
Now you should have a better understanding into how the system reads the QR cards and can employ the best practices as stated above into your photo shoots. If in doubt, remember the following:
- evenly lit
- in focus
Make sure to do all three and your future self will thank you for not having to hunt down and manually tag any more QR Cards.