http://www.bbc.com/capital/story/20170606-you-can-teach-yourself-to-be-a-risk-taker
Optmizing target detection and tracking stability
1- improve contrast
2- avoid repetition
3- check the target histograms in photoshop
4- measure scale for tracking by dividing your camera-to-target distance by ~10: 20 cm wide target would be detectable up to a distance of about 2 meters (20 cm x 10)
5- check the target in gray scale
6- avoid curved shapes