What is the ideal size for a marker?

The size of a marker depends on several factors such as the distance from the subject at which the marker will be placed, the type of lens used with the scene camera (telephoto/wide), and the ambient lighting in the environment. D-Lab makes it easy to determine the right marker size by detecting and displaying markers in real-time. Therefore it allows you to experiment with different marker sizes and find the optimal size for your application.
As a general rule of thumb, the marker image must be at least 20×20 pixels in the scene camera image in order to be detected properly.