Thaum txoj kev xa tawm ntawm qhov kav dej ntau dua los yog sib npaug ntawm qhov nyiaj them siab tshaj plaws ntawm qhov sib koom tes, yuav tsum muab ntau ntxiv dua ob npaug rau cov hlua khi hlua txuas ntxiv mus rau qhov sib npaug zos. Nws yog cai txwv tsis pub kho qhov sib txawv ntawm cov kav dej kom lub pob qij txhawm rau hauv cov kev txwv ntawm kev tawm mus thiab kev sib txawv, thiab nws tsis pub tshaj qhov txwv (Telescopic, xaav, deflection, etc.
