Li-shafts tsa optical tse nepahetseng, hangata ho na le litlhoko tsa ho thatafala holimo.Sepheo sa ho thatafala ha ka ntle ke ho ntlafatsa ho hanyetsa ho apara.Bakeng sa lisebelisoa tsa tšepe, ho thatafala ha boima, ho thata ho feta ho apara.Leha ho le joalo, ha mokokotlo o le thata, o theola boima ba 'mele,' me o theola boima ba 'mele le ho hanyetsa tšusumetso.Ka hona, bakeng sa litlhoko tsa bohlokoa tsa shaft: boima ba ka ntle le boima ba ka hare.