Matches will rarely be perfect,and the owners of the system can vary a sensitivity threshold so as to minimize either the rate of false rejections,which annoy users,or false acceptances,which jeopardize security.

• 对比很少是十全十美的，系统的主人可以改变灵敏度的门限值，以便减少不真实的拒绝（这将使用户恼怒）或不真实的接受（这将破坏安全）。