7x7_100
7x7_100 holds 100 markers of
7×7 bits. In OpenCV it is
cv2.aruco.DICT_7X7_100.
The numbers
| OpenCV name | cv2.aruco.DICT_7X7_100 |
| Bits in a marker | 7 × 7 = 49 |
| Markers available | 100, with IDs 0 to 99 |
| Printed width | 9 cells, border included |
| Bits the decoder repairs | 8 |
| Cell size on a 100 mm marker | 11.1 mm |
| Pixels wanted in the image | 108 (floor 36) |
| Range for a 100 mm marker | about 1.5 m |
Range assumes a camera 1920 px wide, 60 degree horizontal field of view, which is a focal length of about 1663 pixels, and a marker seen straight on.
A smaller dictionary is tougher
7x7_100 repairs 8 bits. 7x7_50 holds the same markers but repairs 9. If you need 50 markers or fewer, prefer it.
When to use it
Seven bit markers hold the most information and repair the most damage, but their cells are the smallest, so they need the closest camera or the largest print.