▁outside ▁their ▁designed ▁range . ▁ ▁Bin oc ular s ▁can ▁be ▁generally ▁used ▁without ▁e y eg lass es ▁by ▁my op ic ▁( near - s ight ed ) ▁or ▁hyper op ic ▁( far - s ight ed ) ▁users ▁simply ▁by ▁adjust ing ▁the ▁focus ▁a ▁little ▁further . ▁Most ▁manufact ur ers ▁leave ▁a ▁little ▁extra ▁available ▁foc al - range ▁beyond ▁the ▁infinity - stop / setting ▁to ▁account ▁for ▁this ▁when ▁foc using ▁for ▁infinity . ▁People ▁with ▁severe ▁ast ig mat ism , ▁however , ▁may ▁still ▁need ▁to ▁use ▁their ▁glass es ▁while ▁using ▁bin oc ular s . ▁▁ ▁Some ▁bin oc ular s ▁have ▁adjust able ▁magn ification , ▁zoom ▁bin oc ular s , ▁intended ▁to ▁give ▁the ▁user ▁the ▁flex ibility ▁of ▁having ▁a ▁single ▁pair ▁of ▁bin oc ular s ▁with ▁a ▁wide ▁range ▁of ▁magn ifications , ▁usually ▁by ▁moving ▁a ▁" zo om " ▁lever . ▁This ▁is ▁accomplished ▁by ▁a ▁complex ▁series ▁of ▁adjust ing ▁l enses ▁similar ▁to ▁a ▁zoom ▁camera ▁l ens . ▁These ▁designs ▁are ▁noted ▁to ▁be ▁a ▁comprom ise ▁and ▁even ▁a ▁g imm ick ▁since ▁they ▁add ▁bulk , ▁complexity ▁and ▁frag ility ▁to ▁the ▁bin oc ular . ▁The ▁complex ▁optical ▁path ▁also ▁leads ▁to ▁a ▁narrow ▁field ▁of ▁view ▁and ▁a ▁large ▁drop ▁in ▁bright ness ▁at ▁high ▁zoom . ▁Mod els ▁also ▁have ▁to ▁match ▁the ▁magn ification ▁for ▁both ▁eyes ▁throughout ▁the ▁zoom ▁range ▁and ▁hold