White Border around Calibration Pattern

[crocis]

I have read in the Kalibr documentation to keep a white border around the calibration target of min. the size of one grid element or the detection might be unsuccessful in certain lighting conditions.

I do not understand how the white border can help in "difficult" lighting conditions. Could explain it?

I am using a ChArUco pattern. Do you recommend to have a large white border also for this pattern?