Pav ca hlau yog hais txog cov hlau 12-300mm dav, 3-60mm tuab, daim duab plaub thiab me ntsis blunt ntug.Cov hlau tiaj tiaj tuaj yeem ua tiav cov hlau, tab sis kuj tuaj yeem siv rau vuam yeeb nkab dawb thiab nyias slab rau dov ntawv.Kev siv tseem ceeb: Cov hlau tiaj tiaj yog cov khoom siv tuaj yeem siv rau cov hlau hoop, cov cuab yeej thiab cov khoom siv kho tshuab, lub tsev siv los ua cov txheej txheem ntawm tus ncej, escalator.